I guess the "Rewrite in Rust" movement is more about using Rust's popularity as an excuse to create community-approved breaking changes and clean-slate designs. PaX Team added the essential security feature W^X to C in the early 2000s, and guess what, this made a lot of application people very angry and been widely regarded as a bad move. But if you rewrite a whole system in Rust, nobody says you break their spacebar-CPU-heating workflow that they depend on.