A U.K. trademark by Total War developer Creative Assembly indicates that Troy is an upcoming location for the Saga offshoot of the strategy series.
The listing, found by Reddit user zhxws simply lists a game called Total War Saga: Troy. The filing was made on July 23, 2019, but neither the developer nor publisher/owner Sega has made an official announcement for the game.
The Saga imprint of Total War is about smaller conflicts, with Total War Saga: Thrones of Britannia releasing last year.
[Source: UK Intellectual Property Office via Reddit, PC Gamer]
Source: Game Informer Trademark Tabs Troy For Next Total War Saga Title