If the data found in the latest version of the Galaxy Wearable app turns out to be accurate, Samsung's next-gen smartwatches will only run Google's Wear OS. The Galaxy Watch 4 and its Active sibling are expected to arrive later this year, more precisely before the end of its second quarter.
https://www.notebookcheck.net/Incoming-funeral-Tizen-might-be-phased-out-in-favor-of-Wear-OS.530369.0.html
It's also possible that this is all to enable WearOS app compatibility with Tizen, if it doesn't already.
As long as Samsung Pay for Gear feature is still available and the smartwatch can keep a really good battery usage, I'm fine with it. I never pay much attention to smartwatch OSes anyway.
If Samsung switches to wear OS they lose me as a customer, I love Tizen especially the ultra low power usage which is why the battery lasts so well.
I won't buy the next Samsung watch if they switch.