The Khronos Group recently announced a provisional specification of OpenXR, a royalty-free open-standard aimed at unifying access to VR and AR (collectively known as XR) devices. Also, Collabora announced Monado, a fully open source OpenXR runtime for Linux.
It appears Valve are truly getting more serious about Virtual Reality as they appear to be making their own headset. On top of that, apparently a new Half-Life VR game is coming.
What will hopefully help developers work on VR projects using Valve's experimental "Knuckles" controllers, Valve have opened up the source code for their Moondust Knuckles Tech Demos.
Valve have expanded their VR support, with the introduction of their SteamVR Input system which is very much like what they've done for gamepads in the main Steam client.
HTC has recently announced that the HTC Vive PRO HMD is now available to pre-order with shipping expected in April, on top of that the normal Vive has seen a price drop.
Keith Packard has been consulting for Valve for the past year to get Virtual Reality devices hooked up and properly working on Linux. Take a look at his presentation from LinuxConfAu 2018.
Serious Sam 3 VR: BFE is another Virtual Reality title with same-day Linux support from Croteam, so those of you with expensive headsets can make things go boom!
Croteam have recently released both Serious Sam VR: The First Encounter & Serious Sam VR: The Second Encounter on Steam. They both use their new Fusion engine which comes with Linux support, Vulkan and 64bit.