Colin Trevorrow was originally set to direct Star Wars Episode IX, but after some disagreements with Lucasfilm (and a bomb in the form of Book of Henry), Trevorrow was removed from the project and hastily replaced with J.J. Abrams. With the film set to come out in a month, it's been revealed that Trevorrow will still get a credit in the film.
According to Collider, the film credit J.J. Abrams and Chris Terrio for the screenplay, but the film has the credit "Story by Derek Connolly & Colin Trevorrow" meaning that some elements of Trevorrow's version may have indeed made its way to the final movie.
Though Trevorrow had been removed from the project, it would make sense that he would still get credit. Phil Lord and Chris Miller may have been fired from Solo: A Star Wars Story, but the movie still had them credited as executive producers. Another director shake-up had Tony Gilroy take over reshoots for Rogue One: A Star Wars Story, but Gareth Edwards still got solo director credit.
For now, it looks like Lucasfilm has a bit of a problem when it comes to picking out their directors. While they seem to be pleased keeping Rian Johnson onboard, they have just lost Game of Thrones creators David Benioff and D.B. Weiss; at least with that project, D&D left before they could start shooting anything expensive.
If anything, Trevorrow is still on the job being hired to direct Jurassic World 3. Star Wars: The Rise of Skywalker comes out Dec. 20.