In The Valley of Gods is a new, fully-fledged, single-player Valve release, though you'd never suspect as much just by looking at it. Of course, though In The Valley of Gods is headed by Valve, it is being developed by Campo Santo, the talent behind Firewatch.
The game was announced a while ago, and though there was some fluster in regard to what exactly would happen to it following Valve's acquisition of Campo Santo, In The Valley of Gods is going through development as planned, with the added bonus of Valve money backing them.
Campo Santo is no longer, for all intents and purposes. The company does still exist, technically, though everyone who worked at Campo is now straight-up a Valve employee through and through, according to Sean Vanaman, one of the studio heads. While this might seem like a regular studio acqusition at face value, it is also a suggestion of things to come.
With In The Valley of Gods, Valve will be back to releasing proper singleplayer games after nearly a decade of stay away from such endeavours. This is, essentially, Valve being true to their promise to release games again, and it's quite a lovely thing indeed.
Granted, there's no word yet on when, exactly, In The Valley of Gods will be coming out, but following the success and ingenuity of Firewatch, it's practically a certainty that the former Campo Santo talent know what they're about. All we can do is hope for Valve to take on more such projects in the future.