Though BB-8 is considered the R2-D2 of the sequel trilogy, R2 has one thing that BB doesn't—a sidekick (C-3PO). News has it that Star Wars Episode IX is going to introduce a new companion for BB-8, and it could be a droid we'd have met in the expanded universe before.
According to Making Star Wars, sources from the set have claimed that BB-8 has a sidekick by the name of D.O. (possibly Dio). The droid is said to be a lot smaller than BB-8 and is said to treat BB like some kind of parent.
What's interesting is, it's possible that this droid could be the same one that works for Star Wars Battlefront II's hero Iden Versio. He starts out as a nameless ID10 droid, but by the end of the game, Iden starts calling it Dio. It even gets a change in color scheme that's almost the same with BB-8's orange/white look.
via; Star Wars Battlefront II
It's still possible that an entirely new droid could be made for this film. If anything, DO is coming out to be the top seller of merch when it comes to Episode IX. Force Awakens had BB-8 and The Last Jedi had porgs; I wonder who the new mascot is going to be for the finale of the sequel trilogy.
We don't have any official synopsis or trailer for Star Wars Episode IX yet, but it's possible that we could be getting our first look sometime around Star Wars Celebration next year. Though a lot of people are wishing we'd get something before 2018 ends, I'm thinking Lucasfilm will leave that space open for a teaser for Jon Favreau's Star Wars: The Mandalorian.
Catch Star Wars Episode IX in theaters Dec. 20, 2019.