You know, I've discussed very similar theories regarding Dumbledore's death with a few friends and a couple people on here... but I am *hoping* that he is an undocumented animagus because the pheonix thing would fit so well into everything.
However, shoould Dumbledore truly be dead, I feel that it will only serve to fire Harry up even more so against Voldemort. Anger/rage is a very powerful force in and of itself.
However, I just can't imagine Harry being able to get through a battle with Voldemort without having completed his 7th year at Hogwarts with an even more amazing Defense against the Dark Arts professor. Do you think he's really not going back? Do you think they're going to close it?
As for Snape.... he makes an awesome bad guy, because I just love to despise him. But I feel its kinda up in the air. I'm leaning more towards the possibility that he's a good guy but they had to set it up to look like he was bad and killed Dumbledore so that Dumbledore could go into hiding and Snape could appear to be a Death Eater through and through. I mean, think about it.... (are you thinking?
) Snape sould have taken Harry captive and taken him with them to Voldemort so Voldemort could get rid of him then and there, but he didn't... he left Harry and instructed the others to leave him alone. Besides, we still don't know the reason why Dumbledore trusted him implicitly in the first place. I'm thinking there's more to the story, but I'm re-reading everything (from book 4 on) to be sure I didn't miss anything...