I'm one of the supposed few that believe snape is on the side of the good. There's a number of clues towards this in the 6th book, and it's the perfect plan. Snape just killed Dumbledore, so Voldemorte would trust Snape with his life.

As for Harry and Voldemorte both dying, I'm also in that group. I think the only way to do a truly happy ending is for Harry to die so he can be with his parents and with Sirius and with Dumbledore. It's the perfect ending that not many people would be expecting.

No matter what happens, the 7th book is going to rock.