C syntax is already way too rich and complex, not to mention the bazillions of gcc extensions required to compile the linux kernel.
Namely, if it has to be "replaced", that would be with something with a much simpler syntax, which will require a bit more of finger power. We don't want to find ourself locked-in by very few compiler vendors (open source or not), that only because it is not reasonable to code a real-life alternative with a small team of averagely skilled devs in a reasonable amount of time.
This language should build on C though: no enum/typedef/_generic/switch/etc, only 1 loop keyword (loop{}) only explicit sized types, no integer promotion, no implicit casts (except maybe void* pointers but number literal casts should be) but explicit casts (compile-time and runtime, without that horrible c++ syntax), explicit compile-time const (we have only runtime consts which could be optimized as compile-time consts), enforce extern for functions (and don't try to put the binary format, elf/coff/etc, semantics into the language syntax or worse, the OS interface semantics), etc.
With enough discipline (and compiler warnings), we could get close to such language.
I did not check the latest and greatest rust syntax, but is what's above its explicit goals?
That said, I am a "everything in 64bits RISC-V assembly with x86_64/arm64 legacy ports kind of guy"... if RISC-V is successful (I wish). We could think of high-level language interpreters (coded in assembly, for instance a RISC-V coded python/lua/javascript/etc interpreters).