A Justice League script has been turned in to Warner Bros. which was written by Kieran and Michele Mulroney (each of whose IMDB stats show virtually no track record as screenwriters). Supposedly the script is so good that WB is shopping around for a director.
Is a Justice League movie going to make it to theaters before your 5 year old graduates college? I wouldn't be on it.
The budget would be monstrous, it would need quite a large ensemble cast where most of the characters would no doubt be marginalized due to the limits of the length of the movie, plus could you get Christian Bale and Brandon Routh available at the same time and willing to put on their respective costumes for this type of movie?
It may happen eventually, but the odds are stacked against it in my opinion. That's not to say that I wouldn't want to see it, of course. Actually over at Cinematical a suggestion was made that they should dump the live-action idea and instead make a big-screen animated CGI version. Now THAT would be cool and a lot more likely to be made sooner, if at all.