Warning: SPOILERS for Deadpool 2 are ahead!
Colossus is among the more well-known members of the X-Men, and he had his time with the superhero team on the big screen in X2: X-Men United, X-Men: The Last Stand and X-Men: Days of Future Past. But since 2016, a more faithful version of the metal-skinned mutant has been appearing in the Deadpool movies, and while he's still an X-Man in this continuity, he's established a "special" bond with the Merc with the Mouth. Wade Wilson will next be seen in X-Force, and while he's not quite certain yet, Colossus' voice actor, Stefan Kapicic, believes his character will be back for this movie. As Kapicic put it:
We still don't know what's going on with the script because he's still working on [Bad Times at the El Royale], and when he's done with that, I think that he's starting to develop whatever he has right now. So nobody's sure what's gonna happen, but I'm not doubting it. I know after Deadpool 2, all these things that are happening in the movie, it's kind of natural to have Colossus be a part of X-Force.
Although Deadpool 3 is in the works, X-Force is the next movie up in this corner of the X-Men cinematic universe, and director Drew Goddard has confirmed that Cable and Domino will return alongside Wade Wilson. As for Colossus, as Stefan Kapicic told Comicbook.com, the events of Deadpool 2 laid the foundation for Colossus to be part of the X-Force team, so if things go as Kapicic assumes, then he'll be added to the lineup as well. It's worth noting that there's already precedence for Colossus to appear in X-Force beyond just his role in the Deadpool movies, as he served on the iteration of the team that was active during the Marvel NOW! era.
With Negasonic Teenage Warhead by his side, Colossus was introduced in Deadpool to try to recruit Wade Wilson into the X-Men and teach him the morality of a traditional superhero. Following Vanessa's death in Deadpool 2, Colossus brought Wade back to the X-Mansion after the Merc with the Mouth's suicide attempt and offered him a spot on the team, which Wade accepted. Alas, Deadpool's time on the X-Men was short, as on his first mission, he killed one of the staff members who had been abusing the children at the Essex Home for Mutant Rehabilitation, and Colossus had to stop him from killing anyone else. Disappointed in Wade's actions, Colossus initially refused to help him, Cable and Domino stop Russell Collins and Juggernaut from killing the Essex House's headmaster, but he later changed his mind and arrived at the scene with Negasonic and Yukio. Now that he and Deadpool are on good terms again, it would make sense to incorporate Colossus into X-Force, although I question if Wade would call the Russian powerhouse right away.
X-Force doesn't have a release date set yet, so stay tuned to CinemaBlend for that information and other updates about the R-rated superhero movie as they come in. For now, be sure to look through our X-Men movies guide to find out what else this franchise has coming up, as well as our 2018 release schedule to learn what's arriving in theaters later this year.