I think the big ones that are absolutely crucial for next gen VR (especially PSVR) are:
Inside out tracking - the HMD can be set up everywhere within seconds and functions very, very robustly + you can imidiatly get a view of the outside world by accessing the video feed of the tracking cams/objects+obstacles could be rendered in your VR environment (much more advanced than WMR HMDs and with 5+ cams to track the controllers in any position)
eye-tracking - the world reacts to your gaze and VR power requirements drop significantly due to foveated rendering
resolution - either much higher res displays or "Varjo bionic display" like overlay of a super high dpi display (in the fovea region, adjusted through eye-tracking) onto a wide fov display
lightweight, self-supporting, robustly tracking motion controllers that sense finger position (kinda already available with Oculus Touch)
added bonus would ofcourse be wireless, yet I think most VR games will still be played standing or sitting, so I don't imagine it would benefit the experience too much and bandwith/ping/stability requirements might be too much for 5G or other wireless connections to handle (+ increased weight/price for batteries, or a charge might not last long) - Laser could work, but has it's own problems like keeping line of sight