I think I'm enjoying this season a lot more now that they have caught up with the books and are doing there own thing. Feels a lot faster paced, plus I'm not so scared to read through forums for risk of spoilers.
On that note, I've had a theory for a few episodes which I haven't actively seen anywhere else yet (although it probably is), and I really think is what will happen:
So Bran can now do a whole load of stuff that even he is still getting to grips with. In an earlier episode, we saw he almost managed to speak to a younger Ned Stark before being taken away by the old three eyed raven. Well, lets assume that with time, he comes to learn that he can indeed talk to people in the past..
He would surely try to fix everything the Lannister's started and try to save his family by going back to where it all began..
So what if he does just that.. he goes back in time to tell the most powerful man in all the kingdoms of everything which is going to happen in hopes he will stop it.
This man believes him and confides in his closest advisors and friends for help. They cant believe what he's saying, and brand him Mad.
Yadder yadder yadder.. enter, The Mad King.
This was just a thought prior to two episodes ago, when Bran had a vision clearly showing us the Mad King for the first time and the KingSlayer stabbing him in the back.
That vision makes me believe this will happen very very much so.
I really, really like this idea.