Well the cancer is definitely back. All but confirmed. But whether that's what kills him I don't know.
With the way S5 was going with Walt increasingly becoming more and more egotistical and ruthless I felt the ending might've involved Walt on his own dying of cancer after losing all his loved ones (through death or them just leaving his life forever)
But the way the season ended with Walt giving up the game and reuniting with Skylar, as well as the opening to the season maybe suggests there will be some redemption for Walt. But I still can't see him alive by the end.
I can definitely see there being some sort of epic Shakespearean tragic ending with bodies stacked up to the wall. The whole show's narrative has been showing the consequences of Walt's actions. From the plane crash to the kid getting shot after the train robbery. The next step is to see the people who are truly dear to Walt's life be killed.
But who knows. The great thing with BB is how unpredictable it is. Who knows what fukkery Gilligan has in store