With the sudden passing of Dumbledore, and Snape's late night escape after the dastardly deed, it strikes me that there is much turmoil among the faculty of Hogwarts. The new faculty roster for Book Seven could be a pertinent detail, and it might signify where help and opposition may come from for the last phase of Harry's quest.
How the faculty shapes up will depend on the decisions of the new Headmistress, Minerva McGonagall. As Minerva is named for a wise and just Goddess, I have confidence in her ability to make astute choices. However, unlike Dumbledore, McGonagall is not in possession of all of the knowledge of current happenings in the Wizarding world. She does not know about the Horcruxes, nor does she know the contents of the Prophesy. She does not, therefore, realize why Professor Trelawney has been kept at Hogwarts these many years, nor does she know, at this point, that Harry does not plan to return. She probably doesn't know that Voldemort cursed the DADA job. At the end of HBP, we are not even assured that Hogwarts will be allowed to reopen. How, then, will Minerva arrive at her decisions, and will they aid or hinder Harry in his quest? How much will Harry deign to confide in her? How large of a role will Hogwarts play in Book Seven, and which students will be in attendance?
The current roster, as of the end of HBP is as follows (kudos to HP Lexicon for its thoroughness):
Headmistress -- Minerva McGonagall
Asst. Headmaster/mistress -- __________________
Transfiguration -- __________________
DADA -- __________________
Head/Gryffindor -- __________________
Head/Ravenclaw -- Filius Flitwick
Head/Hufflepuff -- Pomona Sprout
Head/Slytherin -- Horace Slughorn (for the moment)
Potions -- Horace Slughorn
Care of Magical Creatures -- Rubeus Hagrid/Wilhelmina Grubbly-Plank (temporary)
Herbology -- Pomona Sprout
Charms -- Filius Flitwick
Divination -- Sybil Trelawney/Firenze
History of Magic -- Prof. Binns
Astronomy -- Prof. Sinistra
Arithmancy -- Prof. Vector
Ancient Runes -- Unknown, still present
Muggle Studies -- Unknown, still present
Flying/Quidditch -- (Rolanda or Xiomara) Hooch - first name unconfirmed
Caretaker -- Argus Filch
Librarian -- Irma Pince
Nurse -- Poppy Pomfrey
Professor Flitwick is head of Ravenclaw House, and Professor Sprout is Head of Hufflepuff House. At the end of HBP, after Snape's (apparent) defection, McGonagall asks Professor Slughorn to represent Slytherin House for the time being. She continues at that time in her capacity as Head of Gryffindor House.
However, can she do so as new Headmistress? Dumbledore does not appear to have continued either as Transfiguration Teacher or as Head of Gryffindor House when he became Headmaster. Certainly, by the time we meet him, he has hired Minerva to fill both posts. It seems that both a new Transfiguration Teacher and a new Head of House are needed, along with a new Deputy Headmaster/Mistress and someone to fill our traditional DADA vacancy.
The only teacher, aside from the current heads of house, whose house affiliation we know is Hagrid. Hagrid is a Gryffindor. McGonagall already called him into her office after Dumbledore's death with the other Heads of House. It seems very likely that Hagrid will become the new Head of Gryffindor. This certainly bodes well for any efforts on the part of returning students to help Harry. Hagrid will always do his best to help Harry, and though he has had a tendency to worry about his charges getting into trouble, he is certainly an advocate for Harry and his cause. And his unswerving loyalty to Dumbledore will continue, despite Dumbledore's death. I think that if Harry wants something from Hagrid, he need only say that it was Dumbledore's wish, and Hagrid will move mountains to help him.
I believe that Professor Slughorn will stay on in Book Seven. He is simply too good a character to part with after setting him up so well in HBP. And he is an interesting addition to our collection of Slytherins. What will his presence add to Book Seven? I do not think that Slughorn is a Death Easter, as has been posited. I think that he is a very talented wizard who has the Slytherin shrewdness of mind and penchant for self-preservation. I believe that he'll make the choice that seems the best for him. While it has certainly been proven that Hogwarts isn't as safe as we would like to believe, I think the rest of the Wizarding world will look far more dangerous to Slughorn, and he will stay at Hogwarts, as Potions Master and Head of Slytherin. Though he is doubtful about the school reopening at the end of HBP, he does say that he doesn't personally believe that they are in any more danger at Hogwarts than anywhere else. Will his presence help or hinder Harry? It's hard to say. He is fond of Harry. Dumbledore introduced him to Harry as "an old friend." While Dumbledore isn't blind to Slughorn's weaknesses (and, if fact, makes sure that Harry is aware of them), would he have used that term to describe someone who would try to hurt Harry? I don't think so. Slughorn is one of the few people who knew Tom Riddle as a young man, and he also knows more about the Dark Arts (Horcruxes, etc.) than many other wizards. He could provide valuable information. He is a sentimental man, and his memories of Lily allow him to be manipulated more than once in HBP - and not only because of Felix Felicis. I think that Harry and friends will be able to make use of Slughorn. I don't think he'll try to hinder them, but I do believe that, as in HBP, Harry will have to find the appropriate bait or payoff in order to secure and information or help that he needs from the new Potions Master.
As to a new Deputy, I believe the two most logical choices will be Filius Flitwick or Pomona Sprout. They are the two other teachers whose classes we have visited and whose presence has been felt the most throughout the series. They are Head of House. Of the two, I believe Professor Flitwick will become the new Deputy Headmaster. This will keep the male and female balance between the Head and Deputy Head. Also, Flitwick has yet to really have a moment to shine in the books, and I wonder if we'll see more of his powers and personality with his new position.
A foreshadowing of this new dynamic appeared at the end of HBP, when McGonagall calls the four professors to her new office. This is the first faculty meeting under the new Headmistress. The first question she puts to her counselors for consideration is whether the school should reopen the following year. See how their answers reflect their House qualities:
Professor Sprout (Hufflepuff): "I feel that if a single pupil wants to come, then the school ought to remain open for that pupil."
Professor Slughorn (Slytherin): "Parents will want to keep their children at home and I can't say I blame them."
Professor Flitwick (Ravenclaw): "We must consult the governors. We must follow established procedures. A decision should not be made hastily."
Professor Hagrid (Gryffindor): "Well, I'm stayin'. It's me home, it's bin me home since I was thirteen. An' if there's kids who wan' me ter teach 'em, I'll do it."
The new Headmistress has a diverse chorus of voices to counsel her in her decisions. Their perspectives are all different, but in that scene they begin to form what Dumbledore and the Sorting Hat have been seeking since early in the series: unity of purpose amongst the houses.
Who might be candidates to fill the two teaching openings? JKR has said that, with one exception, she does not intend to introduce new major characters in Book Seven. She says that there is an Order member that we have not yet "properly met." Other than that, our character roster is fairly complete. That means that we have most likely met the witches or wizards who will fill the posts. Let's look at some possible candidates.
Remus Lupin: Remus was, without a doubt, an excellent teacher, and is highly qualified to teach DADA. However, will parents accept a werewolf teaching their students now, any more easily than they would have a few years ago? I doubt it. Besides, Remus is currently up to his whiskers - erm... eyebrows - in undercover werewolf work. With Hogwarts' future already in jeopardy, and McGonagall so new to the job of Headmistress, I don't think she could risk this appointment, much as it would make my heart sing.
Nymphadora Tonks: As a metamorphmagus, Tonks' transfiguration skills are certainly top notch. She is an Auror, so she is a bloody good witch and, presumably, also an expert in defense. McGonagall tells Harry in OotP that no one has been taken into Auror training in the past three years. Tonks is young, so she was probably one of the last to qualify. Would she leave that job to teach? Or, might she take the job as an undercover assignment, and do double duty as Professor and Auror? Her presence could be a huge boon for Harry's side. I think this is a possibility.
However, Harry and his friends need obstacles. Won't some of those obstacles have to be at Hogwarts? Snape is gone. Draco is gone... or, it looks like he is. It's hard to imagine how either could return to Hogwarts after the events on the Tower. Harry really has no antagonist at the school anymore. I don't count people like Filch or Peeves, who thwart everyone with equal malevolence. Tonks, like Remus, might be too easy, and not provide enough friction.
Though it might require the introduction of a new character, one possible way to provide conflict would be to introduce a Ministry official forced on the school by Rufus Scrimgeour in order to try to retain some control of Hogwarts. This might be too much of a referral back to OotP, and Heaven forbid he should send Umbridge back. But a by-the-book, ministry-appointed teacher would provide something for Harry and company to push against, and would cause tension in the school. Percy Weasley? That would certainly cause friction, and might make for some interesting developmental potential.
Or, is it possible that Hogwarts is moving closer to unity, and that all of Harry's obstacles will now come from outside the school? Might Hogwarts become a place to return to between skirmishes, where Harry can recharge and strategize without enemies all around him?
Victor Krum: JKR has told us that Victor will make another appearance in the series. Victor proved himself in GoF as a powerful wizard - good enough to be a Tri-Wizard Champion. He comes from a background full of dark wizards, but does not appear to have taken that mantle up himself. He doesn't respect his old Headmaster, Karkaroff. He does honor Karkaroff's position, though, and behaves respectfully, if not affably to him. To Harry and the other characters he behaves honorably throughout GoF. He attempted a difficult human transfiguration in the second task, which wasn't entirely successful. However, none of the other champions even attempted such a difficult spell. Harry and his friends begin human transfiguration in their sixth year, and all we hear that Harry manages is to turn an eyebrow yellow. Victor is a good wizard. But is he old enough and experienced enough to become a Professor? Possibly. Would he give up a thriving Quidditch career for the anti-Dark cause? Might he come to Hogwarts to teach, allowing him to help revitalize the Order without his move looking suspicious? It would pull him back into the series and make an enormous amount of friction for Ron and Hermione. Again, he doesn't seem likely to become an antagonist against Harry's cause, but he might become an unforeseen and useful ally.
Aberforth Dumbledore: Is Aberforth the 'mystery' Order member that JKR mentioned we will get to know in Book Seven? It's quite likely, though I have always nurtured a belief that Caradoc Dearborn (mentioned only once, in OotP - in the photo Moody shows Harry) was destined to return in some fashion. However, much as I have always believed that the name Caradoc Dearborn was just too good for Jo to have wasted on one passing reference, I have to admit that Aberforth is starting to look more likely. If he is, as we believe, the bartender from the Hog's Head, then we have very few assorted facts to go on. He has made brief appearances throughout the series and has probably been working for the Order under his more influential brother. He is such an unknown commodity at this point it's hard to guess what he might turn out to be. If he is smart and talented, why is he tending bar at such a very unsavory establishment? Is it a cover? Who is he, and what are his talents? By virtue of his relationship to Dumbledore, I have a tendency to trust him, though that is probably not a very wise policy at this stage. Perhaps another Dumbledore will appear at Hogwarts this year.
Bill Weasley: Bill needs a whole editorial to himself, and soon. In the midst of Dumbledore's death, Horcruxes and RAB, Bill's new situation has been almost entirely overlooked on the editorial boards. I think that Bill will meet a great deal of prejudice and fear when he tries to return to his former life. It seems Bill's situation is unique, and no one knows exactly what effects the attack will have on him. So far, the general population of the Wizarding world doesn't receive high marks for bravery, insight or willingness to accept the unknown - people who are "different." Will Bill be able to retain his job at Gringott's? Would McGonagall be any more able to hire him successfully than she would Remus? Possibly. Bill has been a star, both at Hogwarts and after. He is smart, talented, handsome... oh, and of course, "cool." It's possible that McGonagall could quell the fears of the public more easily regarding Bill than she could on behalf of Remus, since Bill won't actually be a werewolf. He is a Curse Breaker, which (as was pointed out in the forums recently) could be a direct link to Harry's needs regarding the Horcruxes. The Horcruxes are nasty things, and it will take a great deal of knowledge and ability to deal with them. Will Bill be positioned at Hogwarts and then be able to lend a hand with the Horcruxes? Would Harry confide in him? Bill has been a sort of hero to Ginny. She clearly adores her oldest brother. Will she help forge a bond between Bill and Harry?
Other characters who have floated through the series include Oliver Wood, Angelina Johnson, Alicia Spinnet, Kingsley Shackelbolt, Mr. and Mrs. Weasley, Mad-Eye Moody, Fred and George (now THAT would be funny...) and various Ministry officials. None of them immediately leaps to mind as a potential Transfiguration or DADA teacher.
Will Minerva also find herself at the helm of the Order of the Phoenix? Or, will whoever is at the helm work with her to ensure that Hogwart's faculty is safely and securely tied to the Order?
One possible source of guidance for Minerva may be the currently slumbering portrait of Albus Dumbledore. The portraits of the former headmasters, according to Amando Dippet's portrait, are "honor-bound to give service to the present Headmaster of Hogwarts." Not that I think Dumbledore would need any binding contract to be willing to give service to Minerva and to Hogwarts. The question is, just how much can he do? Will he be able to tell Minerva all he believes she should know in order to make proper decisions for the school and for Harry? Will he lift some of the burden of decision from Harry, who may be unsure how much to say to his former Transfiguration Professor?
Whether Harry follows through with his plans not to return to Hogwarts will dictate how much influence these new teachers might have on him and his quest. Since we see the books mostly through Harry's eyes, and since I don't believe that Hogwarts can be completely absent from his quest, I think Harry will spend time there. But I think it will be on his terms and that he may or may not take part in regular classes.
How much will he confide in the new Headmistress? I believe that he will use a "need-to-know" basis with McGonagall. I don't think he'll lie to her, but he may refuse to share things, as he did at the end of HBP. I think he respects her, and appreciates her efforts on his behalf. I think either he or Dumbledore's portrait will have to say something about Professor Trelawney and the Prophesy. Trelawney is in grave danger if she leaves Hogwarts, and McGonagall's tolerance (or lack of it) for Divination could lead to Sibyl's dismissal if Minerva isn't savvy about just why she is still there. But I do not believe that Harry will reveal his quest for the Horcruxes to McGonagall - at least not initially. Might he work out a deal with her that will allow him more freedom than others have, based on what he shares about the Prophesy? If McGonagall has had one weakness, it has been a tendency to dismiss insights that have come from Harry and his friends. Will the events in HBP change that? Will she make an attempt to forge a different connection with Harry? And will Harry respond? Will she aid the students that are still at the school in their efforts to help Harry? I expect that Neville, Luna and Ginny, as well as, perhaps Seamus and Dean will certainly return. I think some of the students from other houses, like Ernie, Zacharias and, definitely, Susan Bones will return. What will happen to Crabbe, Goyle and Pansy now that Draco has flown the coop? And how will Blaise Zabini figure in year seven? Ron and Hermione intend to be with Harry, so they will only be at Hogwarts as much as he is.
I would be most interested to hear others' ideas about all of the above, and would welcome a discussion about potential teachers for Harry's final year at Hogwarts.