It's well known that Andor was originally intended to be 5 seasons long, but plans changed after Diego Luna and Tony Gilroy decided that it would be too grueling. Luna first played Cassian Andor in Rogue One: A Star Wars Story, which was released in 2016. Playing Cassian for 5 seasons would've meant that the actor would need to appear the same age he was in the movie over several seasons.
Luna was strongly opposed to the idea, and it was ultimately decided that Andor would conclude after its second season. Many of the show's storylines had to be condensed or scrapped to fit into two seasons, and a possible exploration of Emperor Palpatine's whereabouts before the events of the original trilogy is one of the ideas that was never pursued.
Andor writer Dan Gilroy, who's also Tony Gilroy's brother, revealed that Palpatine's inclusion in the plot would have become inevitable if the series had lasted for 5 seasons. Dan spoke to Script Apart and confessed:
“I can’t imagine over five years we wouldn’t have shown the Emperor at that point. I think we would have got closer to that world. I think we would have gone, like, we're getting a really good sense of opposition forces here but let's go deeper into the power at the moment, the halls of power. I think we would've gone deeper into the halls of power and explored that."
Andor fans are proud of the show for not bringing in characters like Palpatine and Darth Vader. However, Dan Gilroy feels it would've been the natural progression for the story to explore what Palpatine's role was before the events of Rogue One and A New Hope. It would've been interesting and exciting to see how Andor's writers would've handled a character like Palpatine, but they would have likely dealt with Palpatine's political activities and how much fear of the Sith Lord influenced everyone who worked within Imperial Institutions.
Despite not appearing in Andor, Palpatine's presence lingers over every decision taken by the ISB, and he is referred to by name a few times during the show. This proves that it's impossible to completely avoid any mentions of the Emperor if a Star Wars show is set during this particular time period. How can a story set during the reign of the Empire completely avoid the architect behind it?
Currently, Lucasfilm hasn't announced any plans for more stories set during the Rebellion, and Andor may be the last we see of the Rebel Alliance and Yavin 4 for a long time. The next Star Wars live-action project is The Mandalorian and Grogu, followed by Ahsoka Season 2. The Mando movie completed filming months ago; meanwhile, Ahsoka is still filming in London.
Andor is streaming on Disney+.