I would imagine that "good number of people" are mostly Linux hobbyists, and from my personal experience most people use them as a tinkering or IOT device rather than a full-blown desktop due to the lack of performance. If you're mostly in the terminal that's fine, but for running complex web apps a used x86 would make more sense.
I can definitely see that hobbyist market and future Pi-like devices moving to RISC-V, but I'm less certain about mainstream use unless Windows and Mac (or maybe even Android and ChromeOS) really decide to move over.
"Good number of people" is many thousands, maybe even hundreds of thousands.
And I know of 3 families that have pi based desktops at home, and use them as desktops. (One of those has a person that works in IT in it.) I don't know anybody that has "experimental desktops" that they use only to thinker with, AFAIK, when people assembly a desktop, it's because they want to use as a desktop.
The Archimedes was way slower than today's mainstream systems, too. The more applications a processor family gets, the more attention gets paid to making it performant.
I can definitely see that hobbyist market and future Pi-like devices moving to RISC-V, but I'm less certain about mainstream use unless Windows and Mac (or maybe even Android and ChromeOS) really decide to move over.