Just watched the end of part one... Wow. Incredible writing in this show. How huge is the first episode now with Walt buying the gun. Between that and Schroeder seemingly figuring it out, there is a lot to wonder about until next summer...
It'll be interesting to see how it goes. In the last episode, the writers laid a foundation that would allow WW to either return to being the protagonist or continue being the antagonist. It can be written either way (did he really quit?) or (did he remember the reason he started was for his family?).
My guess is that the last half season is going to expose Walt to the other side of the meth business, the users. I believe WW Jr. will likely overdose on WW's meth, and WW will finally realize what he sacrificed for the money he amassed. I think he'll work to stop the production (todd and uncle have likely taken over the operation) while schroeder attempts to catch him. It'll be a race to make things right before he gets caught, and before he dies. I expect him to come clean with Schroeder at some point near the end, and Schroeder to walk away at Walt's insistence (maybe to let him die) for his family. Jesse's role will be interesting as I have no idea how it'll play. He could be killed, forced back into cooking somehow to protect his ex, or walk away bittersweet at the end since he seemingly had the only conscience for awhile.
I'm sure I won't get any of this right as the writing has really been spectacular and mostly unpredictable episode to episode. That being said, I think the writers achieved exactly what they were hoping for as they've got me thinking about what's next...