Rumors of a John Wick cinematic universe first hit back in 2017, not long after the second John Wick film was released. After a massive third entry in the series, a fourth film due in 2021, plus comics and an in-the-works TV series, it makes sense that Hollywood would push ahead on cinematic spin-off Ballerina, too.
Source: io9 – John Wick Is Getting a Female-Focused Spin-Off That Is Somehow Not About Halle Berry’s Character