since we are speculating...I think Dumbledore will die in book six. I've thought all along that these books mirror the original Star Wars trilogy. I see Dumbledore as a kinda Obi-wan influence on Harry. I believe that he will allow Voldemort to strike him down, so that he can start to instruct Harry in ways that he is not allowed to do now. I see Harry as kinda the chosen one or the last hope. If i were writing the books (which i'm not) I would have one of Harry's friends die, probably Nevill, and Harry would see that as his fault. He would start to learn the dark ways from a new instructor who happens to be an ambitious death eater, and would feed on harry's pride... he could rule the world if the were to take out voldemort, or the school is holding him back. he goes to confront Voldemort in his lair and dumbledore dies to show him the right path. It's a strech and probably too adult, but wouldnt that be a good scenario???