https://wccftech.com/ghost-of-tsushima-standalone-expansion-ghost-of-ikishima/

A Ghost of Tsushima standalone expansion called Ghost of Ikishima is currently in development, according to rumors circulating online.

XboxERA co-founder Shpeshal_Nick, who proved to be reliable in the past, revealed today that this standalone expansion in the vein of Spider-Man: Miles Morales and Uncharted: Lost Legacy is targeting a 2021 release. The leaker hasn't mentioned any platform, but it is likely this will be a cross-gen release, which is not surprising considering the main game launched on PlayStation 4. ResetERA forums member KatharsisT also added that it is going to be a single-player expansion.