I think Rust is a competitor for C in much the same way that C++ is a competitor to C. And I suspect it will eventually gobble up more of C's market share than C++ has, because it's a much better language (no disrespect to C++ - Rust is at least 20 years newer), the linux kernel being a good example of this effect.

There probably is still a niche for a simpler language than Rust or C++, but I don't see Go fulfilling that niche. Zig seems like the strongest candidate here.