The more I think about it, the more I think Bale coming back not only retcons TDKR, but the entire trilogy. Nolan spends the whole time basically laying out why being a superhero is a bad idea, because of what happens to Bruce and Gotham because of Batman's existence. It's akin to Watchmen deconstructing the superhero mythos, except Nolan approaches it as if this Batman existed in our world. He basically tells us that superheroes meddling too much in society is a terrible idea. (If Blake is smart, he'll stay on the down low and not make the mistakes Bruce did.)
And then...ZOMG ALIENS WE NEED BATMAN BACK!
I mean, it would be possible, but it would cheapen the very concept
of Nolan's trilogy.