Sources: Christopher McQuarrie Came In To Fix STAR WARS: ROGUE ONE
It's been quiet on the Rogue One: A Star Wars Story scoop front; the gravitational pull of The Force Awakens has allowed that movie to kind of sneak by the collective geek consciousness. We know it's out there but most of us haven't been focusing on it.
That doesn't mean Lucasfilm was ignoring it. The film started with a story by John Knoll - the Chief Creative Officer at ILM and one of the guys who invented Photoshop - and it came into script form at the fingers of Gary Whitta. When Whitta left the project Chris Weitz picked up the baton, but I have heard that even after all those people the script for Rogue One, the tale of how the Death Star plans ended up in Rebel hands, wasn't exactly in the right place. And so Lucasfilm called in a script doctor.
Not just any script doctor! It was Christopher McQuarrie, one of the better writers out there, and a guy who has been called on to quietly fix major motion pictures before (most famously: World War Z). According to my sources McQuarrie came in fairly early during shooting and used his Usual Suspects/Mission: Impossible skills to tighten up and fix this heist story set in the Star Wars universe.
It's unlikely that McQuarrie will get a credit on the movie, although one source used the word 'saved' when talking about McQuarrie's contribution to the film. Is the movie going to be good? We only have eleven months to wait...
UPDATE: it turns out that Latino Review had this story first! Sorry to them for not realizing it.