Digging a little on IMDB, I came across this film:
I am guessing the spectacular response to Avengers should hurry them along ...
In January 2008, Warner Bros. announced the film was on indefinite
hold, allowing options to lapse for the cast. The studio felt the
script needed perfecting, which was impossible because of the
2007-2008 Writers Guild of America strike
Edit 1: Found another link which points to the JLA movie being in the works.
Just yesterday, we brought you the news that Warner Bros. president
Jeff Robinov reportedly stated that the brothers Warner are planning a
Justice League feature film for a 2013 release, after Zack Snyder‘s
forthcoming Superman: Man of Steel hits theaters in 2012.
Today, the LA Times reports that Jeff Robinov has confirmed that the
Justice League script is in development, though he wouldn’t reveal who
was penning the screenplay. The new Warner Bros. president also stated
that the Batman film franchise will be rebooted after Christopher
Nolan‘s impending return to Gotham with The Dark Knight Rises.