A friend and I have been discussing a little theory about something we think is going to happen in the final episodes. I don't know if this is something that others have noticed and discussed on the internet or whatever, but I thought I'd share and get some thoughts.
The theory: Walter is going to kill Skyler.
What makes me believe this is that whenever Walter personally kills someone, he takes on a specific character trait from the killed individual.
If you remember in season 1 when Walter had Krazy-8 tied in the basement, he would bring him sandwiches, and Krazy-8 would tear off the crusts.
After Walter kills him there is at least one scene (I don't even remember which season, sorry) when Walter makes a sandwich and neatly cuts off the crust, just like Krazy-8.
After Walter lets Jane die in her sleep, which leads to the crashing of the airplane, the eyeball from a teddy bear of one of the passengers falls into his pool.
We see several times after the crash that Walter still has the eyeball. I remember one specific instance is in season 4 when we see it in a kitchen drawer at his house.
At the end of season 3, Walter is forced to order Jessie to kill Gale.
As we all know, in season 5 we see that Walter has taken on Gale's love of Walt Whitman poems via a book given to him by Gale, himself.
In season 4 Walter kills Gus Fring...
...and in season 5 takes over his empire.
Early on in season 4 there is a scene in which Walter follows Mike to a bar to try and convince him that Gus needs to go. In that scene Mike orders his drink "on the rocks", but Walter gets his without ice.
After Walter kills Mike in season 5, Hank offers him a drink in the final episode. This time Walter gets his drink "on the rocks."
Now, back up to the first scene of season 5 when Walter is at Denny's.
Here we learn that Walter is using a different last name. Skyler's maiden name--the trait Walter takes from her after he kills her.