Currently, the Galaxy Watch4 series fly the flag for Wear OS 3, which will also be coming to the Pixel Watch later this year. While Google's first smartwatch is not due until the autumn, Samsung has confirmed that the Galaxy Watch4 and Galaxy Watch4 Classic will be receiving a long-awaited Wear OS feature this summer instead.
https://www.notebookcheck.net/Samsung-Galaxy-Watch4-Google-Assistant-availability-finally-confirmed-for-before-Pixel-Watch-release.619252.0.html