I spend 50% of my time writing C and 50% writing Rust.

Rust is gonna win.

What's gonna happen is someone will contribute some fast and loose memory management logic that breaks every single rule of safe design, but, uses a pile of Rust type system shenanigans to make the compiler (eventually) prove it correct... And for an extra 5% page fault performance, no one's gonna care that they need rustc to compile the kernel.

After that it's all a big downhill slide...

Hopefully someone will make the compiler faster though.