According to Hollywood Reporter, Warner Bros. is remodeling its DC Animated Movies line so that they share a single continuity - think of how Marvel Studios built up to The Avengers and you've got an idea of how this will work. WB plans to release two movies per year that will fall into this new continuity, as well as a third film that does not tie into the DC Animated Movies continuity. Batman: Assault on Arkham is slated as that third film for 2014.
Jay Olivia, director of Justice League: War is set to direct. According to the film's IMDB page, Mark Hamill will not reprise his role as Joker, though Kevin Conroy will once again take up the cowl as Batman.