Linux didn't start off competing with Windows, it started off competing with commercial UNIX. (Most people were running Linux on hardware that had Windows licensing costs rolled in.) The price gap between Linux and a "real" UNIX were huge, especially given that you had to buy hardware to match. Is RISC-V really a huge difference in price for any ARM CPU (as opposed to ISA) licensee?
I think RISC-V will quickly infiltrate the invisible on-chip microcontrollers. The ones that manage power regulation, SDRAM calibration training, etc. There is very little friction there.
Then it will slowly enter low cost microcontrollers where cost is absolutely essential.
The high-end will be IMO negligible for years to come.
For full disclosure, I work for Red Hat and am keeping an eye on RISC-V for servers, and I hope it does succeed but there's a mountain to climb and lots of ways to screw up.
But there was definitely a time where Linux was competing with Minix, which was low price (affordable to a Hacker) and had more features.
However its development wasn't done in the open and it was not "free" (in the FOSS) sense, so it's usage in a specific setting (e.g. commercial) was not possible. I guess Linux open license played a huge role in its adoption and not just the fact that it was free as in "beer" (compared to expensive traditional Unix systems) - and within a short time it surpassed Minix features. There might be disagreements about technical choices made (see legendary conversation about kernel architecture), but in terms of features it surpassed Minix in a short time (and today sets the state of the art for commercial Unices).
