Trank had been hired to direct the second spin-off film to follow Gareth Edwards', Star Wars: Rogue One. This comes one week after Trank was not in attendance at the Star Wars Celebration convention in Anaheim, CA. He cited illness as reason for missing the weekend, but with this announcement it might have been a ruse to cover up a problem. This also comes just months before his new adaptation of Fantastic Four hits theaters. After initially expressing extreme excitement, Trank made this statement regarding leaving the franchise:
"After a year of having the incredible honor of developing with the wonderful and talented people at Lucasfilm, I'm making a personal decision to move forward on a different path. I've put a tremendous amount of thought into this, and I know deep down in my heart that I want to pursue some original creative opportunities. That said, the Star Wars universe has always been one of my biggest influences, and I couldn't be more excited to witness its future alongside my millions of fellow Star Wars fans. I want to thank my friends Kathleen Kennedy, Kiri Hart, Simon Kinberg, and everyone at Lucasfilm and Disney for the amazing opportunity and to have been a part of this. May the force be with you all."
Lucasfilm and Disney have already released a statement that production for the spin-off will continue, so I wouldn't be surprised to see a new director hop on board quickly. 
