Despite The Dark Knight being a huge success, most films based on DC Comics have sucked and/or not performed as well as hoped.
Thus, DC and Warner Brothers are going to be announcing a new strategy soon. The word on the street is that they're seeing what Marvel is doing and want to copy that formula.
Thus, plans for a "Justice League" (actually called the Justice League of America, which would be an interesting title for worldwide release) are scrapped for now. That film would've featured multiple characters like Batman, Superman, Wonder Woman, etc.
Now DC and WB are going to focus on films based on individual characters to develop them prior to doing the team films.
That's what Marvel is doing with Iron Man, the Hulk, Captain America, and Thor.
One bit to watch will be if DC follows Marvel's formula of casting the same folks for the individual films and the team film. DC's original plan for JLA was to cast different actors for the team film, which seems really stupid.