This is a thread about a C++ language feature; it's probably most productive for us to stipulate for this thread that C++ will continue to exist. Practical lessons C++ can learn moving forward from Rust are a good reason to talk about Rust; "C++ should not be improved for safety because code can be rewritten in Rust" is less useful.
Especially because many of us security minded folks do reach out for C++ as there are domains where it is the only sane option (I don't consider C a sane alternative), so anything that improves C++ safety is very much welcomed.
Improved C++'s safety means that the C++ code underlying several JVM implementations, CLR, V8, GCC and LLVM, CUDA, Unreal, Godot, Unity,... also gets a way to be improved, without a full rewrite, which while possible might not be economically feasible.