In theory it could happen, but even so it would take years. There’s just so much C code out there. Stuff like Linux, Nginx, Apache, PostgreSQL, MariaDB, SQLite, QEMU, etc etc.

Absolutely not.

C has the advantage of being an extremely small language in terms of syntax, which means its incredibly easy to port it to any architecture. Whenever you build a chip and want to program it, writing an LLVM backend for it with optimizations is almost trivial (assuming you understand the core concepts).

Rust has a lot more things to consider in the compiler, which leads to slow adoption, and also its more cumbersome to program in.