Warner Bros is deep into the process of developing their other DC Comic book properties that aren't going to feature Ben Affleck's Batman showing up in a supporting role.
The last time we heard about "Justice League Dark" (AKA "Dark Universe"), Guillermo Del Toro had left the project. However, Warner Bros was excited enough about his script--not to mention the way the anti-hero team-up entry "Suicide Squad" is being received--to make it a priority. Scott Rudin reportedly boarded the project as a producer to get it in shape to shoot sometime next year.
The Del Toro version of the team, according to the man himself, is Constantine, Swamp Thing, Deadman, Zatanna, and Etrigan The Demon. It's possible that the movie might add in a Cara Delevingne cameo as Enchantress if they want to bring the film closer to the the "Justice League" and "Batman v Superman" universe and DC's "New 52" version of the team included Madame Xanadu.
The lead characters aren't cast, though we've heard Warner Bros is close on a few of the roles.
Guillermo Del Toro wanted Ron Perlman to play Swamp Thing and thus far everyone seems to agree that's still a good idea.
The studio disagreed with Del Toro's choice to play John Constantine and is seeking A-List talent. Right now the frontrunner for the part looks like Colin Farrell, who is currently shooting "Fantastic Beasts and Where to Find Them" with the studio. However, Ewan McGregor has also been approached for the same part.
It's possible that the one that doesn't get the role of John Constantine could fall back to Jason Blood, the human side of Etrigan.
For Deadman, Warner Bros is looking for a comedic presence and for Zatanna, they're still searching for hispanic/black actress to fill the role.
Right now Monica Belluci looks like the top choice to play magic user Madame Xanadu.
The film still doesn't have a director, officially, though the process of making offers and getting pitches is probably well underway if Warner Bros wants it in production as soon as possible.
I have tried to reach Farrell's rep but they have no comment at this time.