I could see them going the route of Robin having already become Nightwing. You could have Batman, Nightwing and Batgirl already established, but with no Tim Drake or Jason Todd in sight. That would be the smartest way to go, in all honesty.
With that said, I posted this in another thread and would like to point out why Robin is so hard to do:
When a movie with their own child superhero can say that and audiences agree, there is a problem with public perception. Sad but true.