U reckon that Ginny will change position, as she was seeker last year, but obviously Harry will return in that position.
Also, I don't reckon Harry will retake the History of Magic exam.He will probably not do too well in it, but he doesn't need it for the Newts. This as well as astronomy? and divination will not be as important.
I reckon that Harry has aced his potions exam. If he hasn't, then McGonnagal will probably somehow talk Snape into allowing Harry to take potions NEWTS, and will tutor him as well.
I also reckon that Harry will go out with Ginny, not Hermione.
Probably there will be more anger from Harry (don't really blame him).
We will find out about Lily Potter's green eyes.
Will Harry be the heir to Griffyndor?
Harry will somehow die while destroying Voldemort (hope not).
Oh, and I hope we see a lot more of Fred and George.
Percy will realise what a prat he's been, and will be accepted back into the family, but maybe not by the other siblings.