Take this rumor with a grain of salt, but the way that Disney+ has been adding numerous spinoff series to its lineup, it’s not out of the realm of possibility.
According to Star Wars Unity, a spinoff for “Solo: A Star Wars Story” is planned for Disney+.
From Star Wars Unity:
While we’ll probably not see a sequel or continuation of Han’s story, I’ve heard a rumor that some kind spin-off set after the events of the movie is being developed as a Disney+ series. As it probably wouldn’t be about Han, Chewie, or Lando; some kind of underworld series dealing with the Crimson Dawn and other scoundrels sounds the most likely.
Back in June of 2018, MakingStarWars reported that some kind of “Mos Eisley” film was in development at Pinewood Studios UK, and it was postponed when Disney changed their stance on the Star Wars spinoff films.
It’s very possible that like with the Obi-Wan Disney+ series, the work done on that Mos Eisley project is being repurposed for Disney+ and that’s what this “Solo” spin-off has evolved from. Lucasfilm never really throws away anything, as stories from the Underworld television series were repurposed for many different things over the last few years.
Due to its disappointing box office performance, there is no way that “Solo: A Star Wars Story” is getting a theatrical sequel, but most fans see it as an underrated film in the Star Wars franchise and it has gained more love after its home video release. That movie is definitely filled with interesting characters and locations that could take place in a potential spinoff series.
So label this one as a rumor for now, but this does seem like it could be a possibility in the future.