My theory is that Bale will do this.
He said he wouldn't work with anyone but Nolan. True. But Nolan is the producer, and often times, the producer's main job is to set the creative vision and, while not replacing the job of the person doing the casting, they often set the tone and direction and that can include finding the main actorsfor the job, leaving the casting director to fine-tune and finalize their contracts. I would guess that Blake would be Batman for a while, but he needs more experience and when Superman comes on the scene, Wayne is called into action. Wayne won't overshadow the current Batman that the public sees, so he creates a newer, rawer version of Batman that can work in the shadow the Blake version, surprising even Supes himself by breaking pattern.
Batman may be what the franchise needs to go over a billion, but how many charismatic actors like Ledger are there who can catch that lightning in a bottle? A billion dollars in box office receipts isn't come by easily. You've got to have repeat viewers for that. Bale's not interested and casting is going to be beyond critical. I was wrong. Snyder is only writing the story. Goyer is writing the screenplay. He wrote MoS. The script had some positives but there were some significant negatives, too. 
