Gary Whitta who worked for a year on the first draft of Star Wars: Rogue One may have left that project but he hasn’t left the galaxy far, far away.
Whitta revealed today that he is writing an episode of Star Wars Rebels. He also changed his Twitter header image to Rebels concept art.
— Gary Whitta (@garywhitta) May 26, 2015
Given the shows production timeline, I would assume this is a season three episode.
It does raise the interesting possibility that one of the Rebel soldiers (Felicity Jones, Riz Ahmed, and Diego Luna) or perhaps the Imperial villain rumored to be played by Ben Mendelsohn could be appearing in the series.