I'm not sure if I think Dumbledore is really dead or not. On one hand, I think J.K. Rowling teaches some decent lessons in the book, and it might be a little... anticlimactic if we learn that death isn't really death. Even if it was just because somebody fixed their death. I know very well that when somebody you love dies, you will try everything you possibly can to deny it really happened, desperately wanting to believe that *something* isn't how it appears, that the person will be coming back to you.
On the other hand, I disagree with the portrait of Dumbledore in the headmaster's office as being "proof." They're portraits of "former headmasters." If Dumbledore has faked his death and left the school to fight bad guys or something of the sort, Professor McGonagall is now the headmistress (or maybe they'll elect a new one). Regardless, he's certainly a "former headmaster," now. Did all of the portraits only appear after retired headmasters had died? Or when they actually retired? I'm not certain we know for sure.
Also, there were a lot of suspicious things going on that night. I refuse to believe that Dumbledore didn't have a good reason to trust Snape, one that we still don't know about. And drinking the liquid... we never really found out what it did. Rowling doesn't usually leave loose ends like that. And the showdown between Dumbledore and Snape seemed like there was more going on underneath than we knew. So, I suppose I'm willing to wait for the next book to see.
