This week, Guillermo del Toro revealed that not only is a Justice League Dark movie in development, but it's what he describes as "very active" development. In and interview with Collider, Guillermo del Toro said, "Justice League Dark is very active. I’m doing one more revision while we wait for the writer. It’s somebody big, [and] we’re patiently waiting for that writer. I think it’s worth it, I think it’s a guy we all admire. I’m doing my revisions on my sort of Bible, on my story for the film. I can tell you it’s the writing project I’ve enjoyed the most in English. Devil’s Backbone and Pan’s Labyrinth are in Spanish, but of all my writing and screenplays, this was so much fun because it was character. It was a pretty easy plot, but the character interaction, Swamp Thing with Deadman and Demon, it’s so joyful for me to write that. Constantine is such a great character, so dry. I think it could be a great movie. I don’t want to do many changes until the proper writer comes onboard."
Based on Guillermo del Toro's answer, it's starting to look like a Justice League Dark movie could make it to theaters before a traditional Justice League movie does. Wonder who the writer is that he's waiting on?