While Suicide Squad wasn't the critical success WB wanted, it did produce the diamond that is Margot Robbie's Harley Quinn, and now it seems the studio might make her the central piece of her own trilogy.
Robbie's Quinn is set to return to the big screen in the upcoming Birds of Prey (And The Fantabulous Emancipation of One Harley Quinn), where she'll for the crux of the team alongside Black Canary and Huntress. According to a rumor (via Geeks WorldWide) the studio is looking to make Birds of Prey the first of a trilogy of Harley Quinn movies, with the mysterious but still in development Gotham City Sirens acting as the second part of the series.
The Gotham City Sirens series in the comics focused on the adventures of Quinn, Catwoman, and Poison Ivy, so having her in that group makes complete sense. If she's struggling between her more villainous and heroic sides, the idea is that these would collide in the third movie, which could be a Birds of Prey v Gotham City Sirens film.
In the comics, the Birds of Prey is made up of Batgirl, Black Canary, and Huntress. Batgirl is also getting her own solo film, so if there is any fuel to this rumor here's how we see it playing out. In Birds of Prey, Harley Quinn manages to get this group together to stop a group that includes Joker (it is labeled the emancipation of Harley Quinn after all). She needs help so she enlists Canary and Huntress for their particular skill sets.
After dispatching Joker out of her life she finds some fellow friends in Catwoman and Ivy, and Robbie has mentioned the relationship with Ivy is one she wants to explore, so that team will gel and will have more in common than Quinn did with her Prey teammates.
In the final film Quinn, Catwoman, and Ivy are set on taking down someone who's a bad person but has the law on their side, and since Harley left the Birds Batgirl has entered that void and become their leader, so both teams will square off due to their opposing viewpoints about the situation.
Granted, that could all be hogwash (ha, I said hogwash), but building more movies around Robbie's Quinn is really a no brainer. As we saw in Suicide Squad, Robbie brought that character to life in a big way and is a merchandising magnet, so regardless of what the movies are called we do expect to see much more of her in DC's movie future.