HBP - I read it in a day when it first came out and haven't picked it up since. It was better, on rereading, than I remembered. Some dodgy plot points, but on the whole not too bad at all. I think it could make a brilliant film.
My predictions for Deathly Hallows? Do you remember 2 years ago lots of readers went 'OMG Snape really is evil, I knew it'? My main prediction for the next book was 'Oh no he isn't' which was a position you had to argue in those days, but isn't even worth mentioning now.
Other than that I'm not sure. I've been wrong about every other book so far. I don't think Harry will lose his powers or die. I think it will all resolve in a not-too-tragic way, with Dumbledore featuring in some way, but ultimately renouncing life in a dignified way, reconciling Harry to the mortality of his loved lost, like his parents and Sirius.
Finally I am hoping that it becomes more obvious to everyone that the wizard world as portrayed in these books is not meant to be exemplary or a utopia, but a satirical criticism of what is wrong with our society and the cruelty and injustice that passes as normal and respectable. At the start of this book Stan Shunpike is still in