The first stand alone spinoff Star Wars: Rebel One already had a director Gareth Edwards and a cast that included Felicity Jones and Riz Ahmed plus Ben Mendelsohn as the villain. According to Variety, Diego Luna has signed on to the project as another rebel fighter.
The story is said to take place between Episodes III and IV, but from the plot description its much closer to Episode IV. Reports say the story is about the rebel fighters who steal the plans for the original Death Star allowing a certain young princess to stash them on an astromech droid.
Star Wars: Rogue One will be in theaters December 16th, 2016.