I mean, it's whenever the devs yank the EA disclaimer off of the store page and call the game "complete." Hypothetically, it could happen tomorrow. It'd make a lot of people upset, but they could probably do it. Though, I think they'll at least shove Mistlands out the door before that happens, and it'd be weird if they don't do something with the Ashlands.

If you are asking for an ETA on when the game will actually have everything the devs initially said they wanted in the game, than our best guess is years from now. The initial expectation was 10 biomes/bosses. Right now there are 5 and none have been added in the ~2 years since the game released into EA. If you buy all of the excuses being made, the rate of progress should be ramping up, so between 3 and 10 years sounds about right. . . . Assuming they actually do make that content and don't give up sooner. See: the start of this post.