You may be right about not doing it now. There's time to do it. But it should happen. It's a fresh and exciting concept.
We've done more than scratch the surface with Batman. But there's an easy 3 or 4 movies you can do now with a Bruce in his 30s(excluding Justice League) of the world's greatest detective. But after that, all the appealing villains will be done so many times over. There will have been enough stories told.
It's about the story and what can you offer that's new. Quality over quantity. The Bond franchise as you think back to Connery, Moore and Brosnan...it was quantity over quality. I don't want the Batman franchise to be on auto-pilot, suffering the same fate.
The key is originality in movie-form. Forget the older comics. We've had our 1939 Batman, our 60s West Batman & Robin (twice now, with the second trying too hard to modernize it and failing hard), the silver-age Batman & Robin adventures, the Frank Miller/Jeph Loeb graphic novels of the 80s and 90s brought to life through Nolan. Now Justice League is another interpretation that's coming soon. The Bruce Timm/Conroy style has yet to come alive with real actors on the big screen so mesh that with the new JLA's. You can pull off a trilogies worth of films, maybe 1 more..but when you go past 4 films you're inevitably going to run it into the ground. Batman Beyond is the next natural step.