According to Jeremy Conrad, a writer for DCEU Mythic, a news website that covers the DC Extended Universe, there are definitely feelers out indicating that a new DC film is in the works and it will feature Harley Quinn and could come to theaters in 2022.
Jeremy wrote, “In talking with multiple sources today I’ve learned that Warner has begun very early talks and discussions about what the next big-screen Harley project will be. There’s absolutely no word yet on exactly what the project is, although I’m sure fans are crossing their fingers for Gotham City Sirens.”
He continued, “A couple of years ago, back before Birds of Prey was really turned into a Harley Quinn movie, there were rumors going around that beginning with that movie Warner wanted to feature Harley in some way every year in a DC film. 2020 is BoP, 2021 would be The Suicide Squad, which means whatever they’re talking about now could end up coming as early as 2022.”
Source : https://www.distractify.com/p/gotham-city-sirens-movie