Several interviews have Nolan saying that he's actually working towards an end to the Batman story instead of the regular feeding an unending amount of sequels like most movie/comic franchises.
there a comic book movie franchise that's gone more than four films without a reboot or remake? The only one I think of, arguably, is Superman...simply because Singer obviously wanted his movie to be a sequel to the first two Donner films....but even then you need to assume that Superman 3 and 4 were retconned away (and, therefore, there was a reboot there too).
In fact, the only unending franchise I can think of outside of crappy horror movies and Japanese monsters is Bond.
