A cancer relapse is possible, if not all that dramatic. Prison would be an anticlimax, and seeing him and his family survive intact, "Sopranos" style, doesn't seem realistic. There's no shortage of people who might want to kill him: Jesse is probably the leading candidate here, although Hank or even Skyler could surprise us.
Do the machine gun and the "Scarface" scene foreshadow a last-stand shootout? Will Walt finally sample his own product and die of a hugely ironic overdose? Fake his own death and sneak off quietly to Vegas?
Series creator Vince Gilligan will likely opt for a climax that's unexpected yet somehow makes sense. Gilligan told TV critics last month that "I think most folks are going to dig the ending."
Let's hope so. In eight more weeks, fans of "Breaking Bad" will finally know everything.