I think Dumbledore is going to be fired. The guy (can't remember his name) from the Ministry of Magic at the end of the fourth book did say he had always sided with Dumbledore, but in the case of him saying that Voldemort had come back, he said he would have to take some drastic measures. I think they're gonna fire Dumbledre, which will leave Harry with little protection and make McGonagall the headmaster of Hogwarts, and she's not quite as understanding and forgiving towards Harry as Dumbledore.
Another thing I'm suspecting is that Malfoy just might join the Death Eaters along with his father as he and Harry grow older. After all, in the 5th book Harry and Malfy are already going to be 15 or 16, a pre-adolescent. By the end of the 17th book, they will both be 17-18 years old. I think Malfoy could be joining Voldemorts side in the final battle, whenever that time will come.