His sales estimates are a little low, unless he's only including PC VR. PSVR alone has sold ~5M units by most estimates. In the most recent Steam hardware survey, about 2% of users that completed the survey have VR devices, which is roughly another 2M users. That doesn't include Quest and Quest 2 sales (many people never use the link cable), or the few Rifts out there that aren't on Steam. So while it's highly unlikely that 6DOF VR devices have sold 10M units, its likely cleared 8M units and could easily surpass 10M in 2021.

The biggest issue right now is lack of software. There isn't much to play at all in VR, and there are very few great VR titles and only a handful of good ones. For HN commenters that want the infinite screen experience, I unfortunately believe that will be relatively niche (you sell to a bunch of programmers) and none of the current players are really focused on enterprise as games have been the stickiest thing so far. Quest 2 is pretty high resolution and eventually a tracked keyboard and infinite office will ship, so it might still be the best option for a while for people looking for VR productivity.