Nobody will rewrite billions of lines of C code anytime soon, especially not in kernel, device driver, or embedded space.
We can already see the damage such rewrites cause in basic user space. Look how slow and bloated Windows UI, UWP apps, Visual Studio, Adobe Reader, Steam (etc) are because of their "rich UI experience." Absolutely horrendous memory consumption too.
Every version of VS gets slower to startup and open even simple projects. I switched from VS to Pelles C for my hobby projects and wow, what a difference. Looks and feels like a real Windows 95 program, the way things should be.
Consistent UI, lightweight, instantly launches and has no trouble keeping up with my keystrokes, unlike VS.
60MB install for the entire package vs multiple GB for a minimal install of VS. Also literally uses a thousand times less RAM than VS (3MB vs 3GB for my current 16 file C project).
You can tell it's probably written in itself as a native Win32 application, like the good old days.