Perhaps mining dips and PC gaming goes back to normal. Alternatively . . .
MASSIVE AMOUNT OF HYPOTHETICALS
If you want to speculate that much, there's a perfectly good cryptocurrency market full of other individuals willing to engage in a lot of what ifs and pie-in-the-sky thinking. Seriously, you're starting to sound like a junkie that needs a new high-end GPU fix or life just won't. It just won't!
If you think the PC gaming industry will wither because of a small number of people who want to play games that are mostly console ports on a high-end GPU won't be able to do that, then I have to question if the PC gaming industry was ever alive to begin with or hadn't died over a decade ago.
Meanwhile, in the real world, the PC gaming market contains a massive number of games that aren't available on consoles and likely never will be. They also don't require a GTX xx80 to run and aren't less enjoyable to play even if you're running them on integrated graphics from an APU. I would imagine most would run on a PC from a decade ago without a hitch.
PC gaming will always exist (and be great) because anyone can publish their games without needing the consent of one of the big three console manufacturers. Most of the games I've enjoyed most in the last five years have been smaller titles from small studios or indie developers that may have never seen the light of day if it weren't for the ability to just create something and put it out there. None of them required a particularly powerful GPU either.