Samsung has officially announced that their next smartwatch OS will be called One UI Watch which is a replacement to their current TizenOS on the Galaxy Watch devices.
This means that their Galaxy Watch wearables will now use Wear OS so your previous apps should be available on the Play Store. And yes, Apps on the Play Store for Wear OS will now work on the future Galaxy Watch.
Of course, apps like Spotify, YouTube Music, Google Maps, and Strava will still be available as there are a lot of applications that are already available on the Wear OS.
Other features that we can expect are auto app installation
The One UI Watch is expected to come out on their next Galaxy Watch device.