Do you really think there are no young people wanting to work on an operating system written in C? I'm very skeptical that all young people interested in operating systems see Rust as the future. I personally feel it's the other way around, it's Google and companies like that who really want Rust in Linux, the young kernel devs are a minority.
It's not that people think that there are no young people wanting to work in C, it's that the number of competent programmers who want to use C, or do use C, are both decreasing every year. That has been the trend for quite a while now.
So there will presumably be fewer and fewer programmers, young or old, that want to work in C.
C is one of the most entrenched and still-important languages in the world, so it probably has more staying power than Fortran, COBOL, etc. So the timeline is anybody's guess, but the trajectory is pretty clear.
There are a lot of languages that people prefer to C which aren't well-suited to OS programming (golang, Java) but Rust is one that can do the same job as C, and is increasingly popular, and famously well-loved by its users.
There's no guarantee that Rust will work out for Linux. Looks unlikely, to me, actually. But I think it's pretty clear that Linux will face a dwindling talent pool if the nebulous powers that actually control it collectively reject everything that is not C.
