>>1201992If I had to guess, though my predictions are usually awful, a new Half-Life game that takes place on the altered timeline where Eli lives but Alyx is kidnapped. However, to showcase the Steam Machine and Steam Controller just as much as the Steam Frame, the game maybe optional for VR and regular gamers.
Either that or VALVe do release Half-Life 3, but comes in two versions. The standard PC/Machine version that takes place after Episode 2 and a VR version that takes place after Alyx. It be the same game, but different story between the two.
But this is purely speculation. VALVe may not be able to count to three, but Half-Life is still their flagship franchise.