Forbes has word from Guillermo del Toro that the script for Justice League Dark aka Dark Universe has been sent-in to Warner Bros. The project has been in-development for sometime but hasn't been given the greenlight by the studio. A major reason it wasn't apart of their DC movie release date slate the studio hasn't actually committed to it yet.
We still have no idea what writer collaborated with del Toro on the script. There is also a bit ambiguity if Guillermo is going to direct or just produce. His next film will be Pacific Rim 2 which is due out in 2017, around the same time as Wonder Woman and Justice League. I think it all comes down to if Warner Bros. commits to the draft they've been given.