Samsung and Google may have agreed to merge Tizen OS and Wear OS, but current Galaxy Watch smartwatches will be left on the older Tizen OS platform. Samsung will update the Galaxy Watch Active, Watch Active 2 and Watch 3 for at least three years from their launch date, mind you.
https://www.notebookcheck.net/Samsung-commits-to-three-years-of-updates-for-current-Galaxy-Watch-smartwatches-but-no-Wear-or-Wear-OS-upgrades.540131.0.html