According to JWFan.net, Nicholas Hooper will not return to score Harry Potter and the Deathly Hallows. Hooper has composed the soundtracks for both Order of the Phoenix and Half-Blood Prince.
The post states that the films have put “too great a strain on his family life” and that he believes a “certain composer” [John Williams] should complete the series he started.
Until we receiver further confirmation, please treat this as a rumor! Thanks to Matthew for the tip!