Well I do think Dumbledore is really gone (when I first read book 5 I thought he'd be coming back but not anymore). I do think that there is going to be some kind of plot twist around Dumbledore's death though. What I can't say, I'm not really sure yet but there's gotta be something going on with that.
I wonder what's going to happen with the whole Nevile/Harry prophecy? I don't have many great predictions yet, I think I need to re-read book 5 first and really think about it.