At Wondercon this past weekend it was announced that the next animated feature film to be released by DC Comics and Warner Home Entertainment will be called "Justice League: Doom.", or at least that is the current working title for it.
The film is planned to loosely adapt the storyline JLA: Tower of Babel by Mark Waid from the JLA comic arc found between issues #43-46. In the comic, the always-prepared Batman compiles files on his fellow Leaguers, including their weaknesses, only to have them stolen by Ra's Al Ghul who in turn uses them to defeat the Justice League of America one by one.
No casting announcements have been made as of yet and it is slated to see released in early 2012.