I think that Snape will be killed as the result of something Harry does or does not do and Harry will find out he was a good guy only after Snape's death.
I'm really scared about what's going to happen. I hope Harry, Hermione and Ron make it through - but I also hope that Dumbledore comes back. I'm afraid that HP really is a horcrux and that he will die.
you all should check out the theories and thread under general chatter all about it. i've a believer in the Harry as a Horcrux theory - and I am not thrilled about it but I do get the feeling he may die.
I am completely on the fence about Snape - he could go either way, really.
I am really excited - I've been re-reading the entire series this summer - I'm almost done w/ number five.