Gotham City Sirens has been said to be in the works with Suicide Squad director David Ayer attached to direct, with Margot Robbie on board as producer and returning as Harley Quinn. The movie has also been said to feature Catwoman and Poison Ivy.
Now the Gotham City Sirens movie and David Ayer being further involved in the DCEU may actually be in doubt.
In a report written up by Mashable, it's noted Comic-Con lacked any mention of Gotham City Sirens, and they further point out that in the Netflix Comic-Con panel for Bright, which is directed by Ayer and reunites him with Suicide Squad's Will Smith, that Ayer slams WB.
Here are the David Ayer quotes from the Bright panel:
While David Ayer didn't specifically mention WB or Suicide Squad, as noted in the above tweets, David Ayer only directed one PG-13 rated movie--Suicide Squad.
Too add to that, a reporter for Variety let loose a tweet insinuating that the Gotham City Sirens movie wasn't even green lit, but that David Ayer leaked the movie so he would still be attached to a DC project.
Per what Ayer had to say above at the Bright panel, and also that he isn't directing Suicide Squad 2, it's pretty obvious heads were butting when Suicide Squad was getting made. While it initially sounded as if Ayer had simply left the Suicide Squad franchise to tackle Gotham City Sirens, there seems to be more to the big picture than that.
It probably also should be noted that WB didn't announce release dates for any of the new DCEU films, so things could always change, and maybe whenever Gotham City Sirens is ready that it will be added to the slate.