Additionally, neither Gotham City Sirens nor this Harley and Joker movie were on Warner Bros’ tentative DCEU release slate from SDCC – which confirmed the titles the studio is prioritizing, including Suicide Squad 2, Batgirl, and Justice League Dark among others.
Warner Bros. is still developing Gotham City Sirens, a Suicide Squad spinoff featuring Harley Quinn, Catwoman, and Poison Ivy.
Forbes, which previously debunked the rumors of a Joker/Harley movie replacing Gotham City Sirens, has further confirmed with Warner Bros. that both films are currently in development.
Reports on the Harley Quinn/Joker movie indicate it will be released following Suicide Squad 2, and we can assume Gotham City Sirens will be sometime after that.