Some of the voice cast of The Dark Knight Returns, Parts 1 and 2
have been revealed: Peter Weller as Batman, Wade Williams as Harvey Dent/Two-Face, Michael McKean as Dr. Wolper, Ariel Winter as Carrie Kelly/Robin, and David Selby (whose part hasn't been announced yet, but it's probably Alfred). Voice casting for Gordon, the Joker and Catwoman is yet to be announced. Jay Oliva is directing and Bob Goodman wrote the scripts.
The first part will be released in fall 2012 and the second part in early 2013. The banner for DC's animated movies is reportedly changing from DC Universe Animated Original Movies to DC Comics Premiere Movies as of these two releases.
You can see images from the movies here