Thought as it was brought up today and a few people were asking questions in chat if may be a good idea to post some info on this game.
It's a stand alone game from the original Subnautica.
"Content Complete" is a large patch that was expected to drop today (31st October, 2019) but has been delayed until mid November.
Content complete will not contain the final 2 acts of the story, they are expected to be released on Offical Release 1.0
Some useful links:
If you are looking for more timeline information, you can view the Below Zero Roadmap here: https://unknownworlds.com/subnautica/be ... -timeline/
You can also view the development site (Favro) here: https://favro.com/organization/35200a08 ... 91bb14c708
CAUTION, the Favro contains a lot of information that may be considered spoilers. There are no direct story details but if you don't want to see vehicles, models, biomes, that kind of thing then avoid this.
There's also the wiki here: https://subnautica-belowzero.fandom.com ... Below_Zero
Basically all information on everything we know so far can be found here, if you don't want any kind of spoilers best avoid, there is some early story info that is currently in the experimental version of the game.
Hope this helps some folks.