One, it’s not the game you probably expect (or want), and two, this is according to an unverified leak, so maybe it doesn’t even matter.
Assuming this transcript of an unpublished interview between The Game Awards host Geoff Keighley, Valve developer Robin Walker, and a third unidentified person (Gabe Newell?), is for reals, the studio is prepping to announce Half-Life: Alyx, a new VR game, at the show on 12 December.
The source of this document is credited to one “Midoriyan”, allegedly the same guy previously responsible for leaking info about DOTA Underlords, although I can’t find a reference or link to this alias anywhere else. Valve, however, has also confirmed a “flagship VR game”, whatever that means, for launch in 2019.
At publish time, Valve has not confirmed this leak, but that’s kind of how Valve works.