I believe for the next Half-Life, latest rumors indicate it is actually back to 2D. During the press event last month, they were also pretty clear that no VR game is currently in development at Valve.
A huge missed opportunity imo, but maybe playing HL3 on a theater sized screen is nice enough.
Some rumors from ~1yr ago indicated they were looking into making it an asymmetric co-op game where one player would be Gordon Freeman on PC and one would be Alyx in VR. Of course, they could have dropped that by now.
I'm sure they've tried making it hybrid, aka VR optional. I'm curious if they'd be able to make it work. If not, I don't expect a VR only HL game again.