Hopefully Zig [1] language will become a better alternative to C in upcoming years. Not talking about higher level code where Rust or Go can be a better choice.
No language can become an alternative to C in the context of UNIX like OS because no one is going to re-write them from scratch, given their symbiotic nature.
Even if the complete userspace of Aix, HP-UX, *BSD, GNU/Linux, OS X, iOS, Solaris,.... gets re-writen in something else, there will always be the kernel written in C.
Hence why improving C's lack of safety is so important to get a proper IT stack.
The problem with Zig is that they changed almost everything. I think there's a high risk they introduced new design problems that we won't know about fully until Zig has been used in anger for 10 years.
I've always felt that C is near the sweet spot. I'd rather see a minimal change to C that broke backwards compatibility (because it has to) and fixed the top ten simple problems.
Even if the complete userspace of Aix, HP-UX, *BSD, GNU/Linux, OS X, iOS, Solaris,.... gets re-writen in something else, there will always be the kernel written in C.
Hence why improving C's lack of safety is so important to get a proper IT stack.