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.
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.
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.
A huge missed opportunity imo, but maybe playing HL3 on a theater sized screen is nice enough.