Roblox has the userbase it does because it's on every platform and runs on potatoes.
How many kids (using a large range from ages 1-18) have VR setups in their homes?
Can't answer this directly but recently the multiplayer VR games have had more 10-16 year olds than any other group
I have a Valve Index ($1,000 + gaming PC + installing 2 lighthouses on my walls), and while my experience is definitely better (other than the cord), the Quest provides a comparable experience for beat saber, rec room, pistol whip, which comprise 90% of what I use my Index for anyway.
If VR fails at this point I would be surprised. If Facebook got some competition it would be good for long term VR development. But there's already a good amount of VR hype and great games and it won't be going away anytime soon.