Obviously it's not going to be a happy ending. I don't think there's going to be a huge main cast body count but obviously the main cast won't get through unscathed either. But somehow I see Jesse as possibly getting out with a decent life, more likely than the Whites and Schraders. I know they were going to kill him in season one if it weren't for the writer's strike, but at this point it just seems like his arc.
Secondary characters, though. Lydia, Todd, zero percent survival chance.
I think the season is going to focus around Hank trying to protect his family from the fallout of Walter's crimes. His first impulse will be to want to come after him, then his next impulse would be to make Walter go away without destroying Walter Jr's life.
My estimation of survival percentages for the main cast:
Walter Jr 99%