My guesses in order of likelyhood
1. Killed by Jesse.
2. Killed by Hank
3. Killed by Lydia/Todd/the rest of that gang
3.5 The Mexican Cartel gets him
4. Arrested by DEA
5. Cancer takes him
6. He survives, broke and alone.
Doesn't hurt to have him available for future spinoffs.
I say he ups again with Lydia and Todd gang who will kill Hank and Jesse. The DEA will then take care of Lydia and that gang when they follow the drug manufacturing trail that they left when they took all the material from the guys that they killed in the desert operation when Lydia was there trying to get them to come with her. Skylar and Marie will end up at Marie’s with the kids. The only one that is left is Saul, the lawyer, who will get Walt another new identity for the right price. He’ll use that to leave after the dust settles and off he’ll go into the sunset. We’ll never know when he dies.
Maybe he lives out the rest of his days lonely and broke.
Broke because the coordinates to his stash was made into lottery tickets, which he hung up in his house, maybe they get burned up when (and if) Jesse torches the place.
Just a theory! :)
Another possibility is Walt sitting on sacks of money all alone on a remote island watching the sunset. The Midas Touch, everything he has touch has brought misery to the people he loves. When you deal with the Devil, well.....
Read that the writer said in an interview that the ending would be a bang up total surprise
..and that we’d be pleased.
re: #6, what of the buried cash?
So...Will Hank become a zombie and eat him?