Originally Posted by kane

I have two guesses.

1. With Gus out of the way Walt cashes in big on the meth market. Makes some serious money and is then caught by Hank. Hank, however, realizes that Walt and his meth money have paid for his medical bills and rehab etc so he either lets him go or he offers him witness protection and has him testify against other guys Walt has dealt with (possibly including Jessie).

or

2. Walk makes a bunch of money, Hank finds him out and is going to arrest him. Walk kills Hank and the final season ends with Walt finding out that his cancer is not only back, but that it has spread and this time there is no hope.