https://gamedaily.biz/article/1337/report-oculus-quest-has-s...
And it seems VR sales (EDIT: shipments) are hovering at around 6,000,000 a year (this tends to include the crappy VR headsets that are sometimes given away for free with high end phones).
https://www.androidcentral.com/nearly-half-all-vr-headsets-s...
This sounds like a lot...but it might not be. To put things in perspective, the Kinect sold around 20,000,000 units and was considered a failure by Microsoft which is why they abandoned it. I think the parallels between the Kinect and VR is worth noting, since most are really accessories to something else (or used for very niche purposes).
VR definitely isn't mainstream yet, but it might get there in a few years. I think Half Life Alyx will be an interesting juncture and maybe even a make-or-break point for VR.