Sucker Punch seems to be working on Ghost of Tsushima 2
A bunch of job listings suggests so.
Ghost of Tsushima had a troubled development that dragged on for a long time. The game proved to be really good though and was also a major hit for Sucker Punch and Sony. Therefore, most people assumed there would be a sequel made eventually, and judging by recent job listings, the work has already started.
Sucker Punch is currently looking for an encounter designer for an unspecified title. But at least we get to know that this person will work on "an open world game, with a particular focus on melee combat and stealth" - something that undoubtedly is the perfect description of Ghost of Tsushima.
As Ghost of Tsushima was released two years ago and this position implies that the project has already entered full production, it hopefully means that a reveal isn't too far off. Perhaps during The Game Awards in December?