Creative Assembly, the creator of the Total War franchise, is working on a "new franchise," per job listings on the studio's website (H/T SegmentNext).
In fact, both Creative Assembly and its publisher, SEGA, have posted several job listings that indicate the studio is hiring for "a new project, as part of a new franchise." The description for the senior gameplay programmer position says the game will be made "on top of Unreal Engine 5," making it the studio's first using Unreal. The descriptions also refer to a science fiction setting.
Science fiction isn't far from Creative Assembly's bailiwick. The studio released Alien Isolation, a first-person survival horror game based on the Alien franchise, in October 2014.
Although it's possible these listings could be tied to the studio's next game based on the Alien franchise, other listings for work on that game explicitly referred to the franchise. That these new listings make no such reference indicates they're likely for another project.