According to an interview with IFMAGAZINE.COM, WATCHMEN director Zack Snyder would like a crack at the classic graphic novel, THE DARK KNIGHT RETURNS:
“I’m interested in Frank Miller’s [graphic novel] THE DARK KNIGHT [RETURNS]. That’s really my favorite comic book. However, the studio has this massive franchise and I don’t think they’ll let me make a Batman movie where he’s 50 years old and Ronald Reagan is president.”
Personally, I'd like to see the current franchise continue as opposed to a one-shot, alternate continuity film. However, I will admit that Zack Snyder is high up on my list of possible "Bat-Directors" if and when Chris Nolan finally steps away from the franchise. I also wouldn't mind TDKR adapted into one of those DCU PG-13 films that are currently producing.