The Cassian Andor one of many shows Lucasfilm has in development.
After the untitled Cassian show was announced, it was revealed that The Americans' pushed back when Cassian's show was going to begin filming, but Lucasfilm is working to get the series ready by adding more cast and solidifying the creators involved.
Today, Stellan Skarsgård and Kyle Stoller ing the series and revealed Genevieve O'Reilly is returning as Mon Mothma. O'Reilly played the Rebel leader in Rogue One opposite Luna, with Denise Gough also ing the series in an unknown role. Meanwhile, Lucasfilm confirmed that Tony Gilroy is taking over as showrunner on the series, with Dan Gilroy (Nightcrawler) and Beau Willimon (House of Cards) ing the series as writers.
The return of O'Reilly as Mon Mothma is not completely surprising, but this is a welcome confirmation. Mon Mothma was originally played by Caroline Blakiston in Star Wars: Return of the Jedi, with O'Reilly taking over the role more recently. Although O'Reilly received her biggest role as Mon Mothma in Rogue One, she was first cast in the role for Star Wars: Episode III - Revenge of the Sith but her scenes were cut. She's also voiced the role in Star Wars Rebels. However, Mon Mothma's appearance in the Cassian show could give her the most screen time she's ever had.
Mon Mothma isn't the only familiar character confirmed to return opposite Cassian in the series, as Alan Tudyk was previously announced to be returning as K-2SO. With a few known characters already included in the cast, there is the potential that more will be revealed later on. Jimmy Smits would be a logical candidate to return as Bail Organa, while other Rebels like Alistair Petrie's General Draven could also appear. Hopefully more announcements will come as production on the Cassian Andor Star Wars series continues to inch closer.
Source: Lucasfilm