Rewriting bits of the kernel makes sense. I can’t imagine them porting much C# to Rust though, beyond very small, self-contained services.

Everyone likes a dramatic headline, but in my estimation there is 0% chance of Microsoft pushing widespread Rust adoption over C#.

In the long-term I’d guess they are more likely to continue extending C# with features that make it possible to optimise hot loops. They already added NativeAoT and ref structs, and they have done a lot of research into memory regions and capabilities (an alternative to Rust’s affine types).

Eventually it may be possible to opt into a clunky language subset that gives Rust-like performance without giving up memory safety.

They are also quite likely to use OS-level intervention to safely sandbox C++ code inside a .NET process without giving up performance. They’ve done a lot of research on this, and now they can steal notes from webassembly too.