Dwarf Fortress goes on sale on steam on December 6th. The price is currently unconfirmed.
Going to resolve this based on follow-up to Tanya's tweet.
Just from the diehards buying it day one it should be comfortably trending, plus it's got the kind of word-of-mouth and gamer legend that even some major studios can only look at with envy. It is fairly niche, but I'd expect its launch to be roughly equal to Rimworld's and I think they went well over this mark. I suppose the price point is a possible source of failure . . .