Walt will die for sure. The writers have basically confirmed that. If you think about it, he's a had a death sentence all along. Before we thought his enemies might kill him, we thought he'd die of cancer. One way or another, its pretty much the "destiny" of his character.
I think the only question is who else are they going to kill. I could see anyone going, really... Hank, Skylar, Walts kids, Jesse. I think the most interesting will be what they decide to do with Jesse. So far he's been a pretty tragic character. Are they going to let him overcome in the end and live, or kill him off just when he was turning his life around like a true tragic character?