I'm pretty sure that Dumbledore isn't going to come back to life. J.K.R has always made it very clear that death is final, even in the wizarding world. I think the significance of the pheonix leaving was that Faux (sp?) was loyal to Dumbledore only, and now that Dumbledore was gone, the phoenix left. I agree, Faux seems important to the plot somehow... maybe he'll follow Harry around and help him now? Maybe Dumbledore left Faux to Harry in his will, if he had one? He'd be very useful, with the healing tear drops, and he could make Harry feel better with his song.
As for Dumbledore planning Snape's betrayal, I have a post somewhere above saying how I feel about that, if you want to read it. Of course, that theory is seeming a little bit obvious now, and J.K's never obvious. I think that there is much more to this than we know. Maybe Snape made an Unbreakable Vow with Dumbledore, saying that he would alwas be loyal and obey him?
It's R.A.B actually, lol, and the theory is that it's Sirius's brother, Regulus Black. This too, however, is getting a little obvious, and I think it's too easy of a guess. So basically I have no idea as to who it could be, lol.
Not really sure what you mean on this last question. Dumbledore told Harry that the prophesy didn't have to happen: it started becaue LV heard it and gave Harry powers. From what I get out of it, Harry could turn his back on the prophesy, but LV would still want to kill him, so it would still end up being 'neither can live, while the other survives...'. And the prophesy will come true because Harry wants Voldemort gone, and will try to finish him off, whether or not there's a prophesy. But the prophesy isn't law, and many prophesies go unfinished, this one won't only because Voldemort heard it in the first place.... does any of this make sense
? It's very hard to explain.
Well, there's my take on your questions. Hope that was helpful.
Oh, and if you want to see Emerson (webmaster of mugglenet) and Melissa's (webmaster of The Leaky Cauldron) interview with J.K Rowling, it's
here.
J.K is so funny!! Sorry all you Harry/Hermione shippers!