This isn't something that's coming soon to a theater near you (unless of course there's a sudden groundswell of support from the Internet or something), but Dark Knight Trilogy producer and The Boy Who Loved Batman author Michael Uslan said in an interview late last week that he would like to see a Batman Beyond film get made.
At last week's world premiere of Batman: The Dark Knight Returns Part 2, Batman on Film reports that Uslan advocated for the idea, saying, "Now if I could put my 'fanboy hat' on, not my 'producer hat.' How cool would it be to see a Batman Beyond move? Bruce Wayne in his 80s training a young Batman. And how cool would it be to see Clint Eastwood as Bruce Wayne in his 80s?"
A similar premise, ironically enough, was in development as a live action film before Batman Begins found traction at Warner Brothers.