> It seems obvious that with hardware-level memory safety on the way[1], just gradually modernizing existing C and C++ codebases to take advantage of safer constructs (like smart pointers or checked arithmetic) makes much more sense than rewriting everything in Rust

I read this in the opposite way: if the hardware is going to be stricter about memory accesses being valid, that suggests that software is going to have to meet a higher standard in order to successfully run.

Imagine if you had to satisfy the Rust borrow checker, except you're still writing C and don't have additional tooling during compilation to show how a problem could trigger, you just have more crashes.