Valve insider Tyler McVicker (former ValveNewsNetwork) says 2 Half-Life games are in development...
One of the two game is Citadel, who supports both VR and non-VR modes and the second one is Half Life: X (just a codename for now).
Since the rest is in his Patreon, I can't share more information for now.
Citadel is, apparently, a multiplayer game that pits VR and M&K players together.
The game so far is looking to be a Zombie Master type of thing,