Even with the loss of Joss Whedon, Warner Brothers is continuing to develop his Batgirl project alongside the Harley Quinn and Birds of Prey solo movies. Variety film reporter Justin Kroll wrote on Twitter that there are two versions of the Birds of Prey script, both containing Barbara Gordon's Batgirl (currently uncast) and Harley Quinn (Margot Robbie). While the studio was searching for a director earlier this month, they seem to have settled on Cathy Yan (Dead Pigs).
One of the scripts is from Christina Hodson (Whedon's replacement on Batgirl), although it could just be her treatment for the Harley Quinn spinoff, which featured the Birds of Prey. Moreover, Kroll's tweets state that the BoP team-ups in both scripts differ other than the constants of Gordon and Quinn. Nevertheless, the studio was so impressed by Hodson's screenplay that they decided to do Birds of Prey first and push off Suicide Squad 2, which was reportedly going to start filming this year. Kroll asserts that the sequel will still be entering principal photography "almost immediately after" Birds of Prey is finished shooting. It is unclear whether Suicide Squad 2 (directed by The Accountant's Gavin O'Connor) will still be released in 2019.
Moreover, Warner wants to introduce heroes like Batgirl in an ensemble piece before giving them their own films, similar to what Marvel did with Black Panther in Captain America: Civil War.
In the comics, the original lineup included Batgirl, Black Canary, and the Huntress, but also extended to characters such as Lady Blackhawk, Big Barda, Jade Canary, Gypsy, Hawkgirl, Judomaster, Manhunter (Kate Spencer), Misfit, Hawk, Dove, Black Alice, and Power Girl. When the team was first introduced in the mid-1990s, Barbara was wheelchair-bound in keeping with the fact that she had been shot in the spine by the Joker in The Killing Joke (1988). With the codename "Oracle," she was still able to be of use to Batman and her fellow Birds of Prey by conducting researching and offering useful advice while they were out in the field.