I don’t have the same aversion you do about a Dark Knight Returns movie, but I agree with Old Timer—they wouldn’t jump to a old Batman in the next movie anyway.
Of course they are going to finish off the Year One movies with Bale. But where will they take the Bat after that film is finished? With the success of The Dark Knight Warner Brothers is jumping on the superhero bandwagon. There is talk of a Superman reboot, Justice League is back on the table, and there is work on a Green Arrow movie that has him in a supervillian prision called Supermax. I’m still hoping for a Superman/Batman film, but I wouldn’t mind a Dark Knight Returns movie either. Personally I really want to see a Green Lantern movie.