Update: The Exegol element of Deadline's story has been refuted by Borys Kit, who broke THR's report on the film. We've kept a few references to the planet in our story below just for clarity, but otherwise expect the movie to be set elsewhere.
Just a clarification: The new #StarWars project does not take place on Exegol. I wrote a casual and fun line regarding plot details being unknown but tied it to the subject matter (I do that sometimes) and Deadline has taken it and run with it. https://t.co/qeU496aVFfFebruary 21, 2020
Original story: The existence of a new Star Wars movie has been reported by multiple outlets, and it's apparently set on the Sith planet of Exegol. The unnamed film could come to either Disney Plus or theater screens, and it's reportedly got both a writer and a director attached already.
THR was the first to break the news, explaining that JD Dillard, the director of acclaimed 2016 sci-fi picture Sleight, is down to make this new movie. Matt Owens, a writer who worked on the shows Luke Cage and Agents of Shield, is apparently scripting it. Deadline then published a report that mentioned the Exegol detail.
This hasn't been officially confirmed or announced by Lucasfilm, so keep that in mind. There's not much more to the story right now, other than it's apparently not associated with the Star Wars movie being produced by Marvel CCO Kevin Feige, or Rian Johnson's previously-announced new trilogy of movies.
As both outlets note, it's plausible that any new Star Wars movie could be considered for Disney Plus, given how massively successful The Mandalorian has been on the platform. The next Star Wars theatrical movie officially on the schedule is releasing on December 16, 2022. We don't know what that film is yet, or who's directing it.