In exactly 6 days, the Galaxy Watch 4 and the Watch 4 Classic will be released sporting Wear OS 3 by default. Rumours speculate that the Galaxy Watch 4 series will support both the Google Assistant and Bixby.
Google Assistant was created by Google, as the name states, and Bixby was created by Samsung. The 2 assistants support the Galaxy Watch 4 is mainly because both Samsung and Google were involved in the making of the device that will come out on the next Galaxy Unpacked on August 11.
Samsung made sure that the UI wasn't entirely Google by making it so it would be covered with a layer of One UI Watch 3.5.
To activate one of the assistants on Wear OS, long-press on the crown.
What's really interesting is the fact that while looking in the unofficial Galaxy Wearable app, 9to5Google found a file named com.google.android.wearable.alternate_assistant, which could point out the fact that Samsung may be in the middle of creating a new assistant. Users will be able to choose which assistant they would like to use, yet this new assistant that hasn't been revealed may be in the options.
The full specs of this device can be found here.