When the Los Angeles Times interviewed Warner Bros. president Jeff Robinov, they speculated on the future of DC Comics' properties and believed a new Justice League film was in the works. They stated, following the 2011 launch of the Green Lantern film, Warner Bros. are "to release new Batman and Superman films in 2012 and Justice League, a teaming of DC's top heroes, in 2013." However, there is no official word if the film is happening or not and how the Superman film being pushed back to the summer of 2013 would affect it. However, it was later announced that the film may be released in 2015.
And under the Batman heading:
With the conclusion of Christopher Nolan's current trilogy, Warner Bros. is rumored to be producing a Justice League film, targeted for a 2015 release. With the Batman franchise being revamped to fit into the Justice League universe, Nolan and his wife, Emma Thomas, will stay on as producers for the project.
From wikipedia Justice League article -
At the 2013 San Diego Comic-Con Zack Snyder, director of Man of Steel,
confirmed an upcoming sequel for Man of Steel currently known as
Batman/Superman, though the official title is yet to be announced; the
movie is slated for release on July 17, 2015. The film will star Henry
Cavill reprising his role as Clark Kent/Superman and many of the first
film's cast are set to return. Ben Affleck will also join the cast as
Bruce Wayne/Batman. Flash and Justice League films are rumored to be
released in 2016 and 2017 respectively