We've left it until the last minute to tell you, because we wanted to be absolutely sure it will happen: Subnautica is releasing on Xbox on the 17th of May, at 12am your local time.
Subnautica is available on Xbox as a 'Game Preview' - This is a way of saying 'This game is in the early stages of development.' It's not finished. In fact, the Xbox version is (for now) a little way behind the Steam version.
Just like the Steam version, we will update Subnautica on Xbox regularly. Our first task is to add the Farming & Machinery updates. To receive Xbox specific development updates, follow the Subnautica Xbox Twitter and Subnautica Xbox Facebook pages.