At an interview in NY, JK confirmed 100% that Dumbledore is indeed dead. But, I think that he might still make some sort of appearance or presense. Maybe something like how Obi-Wan appeared to Luke. Or, maybe even just in a letter or something that he left before for Harry. One of those, If you are reading this than I am probably dead, type of deals. (Am I pushing it here )
One thing that I think will happen is that Snape will die. I honestly can not see how he will live throughout the last book, regardless of which side he really is one. Makes me sad to think about though...