Disney and Lucas Film have announced that Director Colin Trevorrow will be exiting as head man behind the untitled Star Wars Episode IX. It was a very short statement, amounting to only three sentences on the official Star Wars site:
Lucasfilm and Colin Trevorrow have mutually chosen to part ways on Star Wars: Episode IX. Colin has been a wonderful collaborator throughout the development process but we have all come to the conclusion that our visions for the project differ. We wish Colin the best and will be sharing more information about the film soon.
Trevorrow's most recent work, Jurassic World, earned a ton of money at the box office despite the film's acting being horrid. That is not a reflection of his work, however, and excitement was high to see what he could do with Star Wars. He has been signed as Director for over two years, but Jack Thorne was recently brought on to replace him as writer.
The film is currently set to release on May 24th, 2019, leaving the December release window most recently set with The Force Awakens. The first six films all released in May, so this isn't anything new. We'll have to wait and see how this pans out, as it appears the script is being rewritten nearly completely.