At a shareholder meeting earlier today, Warner Bros. announced a huge slate of films based on DC Comics characters, including a standalone Wonder Woman film, and two Justice League movies.
Notably absent from the announcement was any sign of the Justice League Dark movie that Guillermo del Toro has repeatedly said is still in development and that he is still working on.
Fans have been concerned that the film would be shelved due to the existence of the Constantine television series, which seems to tread the same ground. Del Toro has said before that his film and the Constantine TV show are not connected, but that the film is still moving forward, in the past. Of course, recent comments from David Goyer, asserting that a version of Justice League Dark will appear on Constantine, may make those questions worth asking again.
A key thing to note is that Sandman was also left off of today’s announcement list. In the same interview reference above, Del Toro said that Warner Bros. wanted to keep Justice League Dark and Sandman separate from the core crop of DC Comics films (and each other) until they felt both properties had proved themselves viable, and that they would then merge them into one. So perhaps the Justice League Dark movie is still in the works, but was simply unannounced because it’s not considered to be related to the other films that were announced at this point.
These seem like to the two most likely answers. Either the film was cannibalized and shelved to feed Constantine’s burgeoning mystical universe, or it just wasn’t invited to the party. There’s no way to know for sure until Warner Bros. either officially announces the project, or they or Del Toro officially declare it dead.