Don't get me wrong: C++ sucks. But as far as Rust goes you are way too optimistic. In the context of game development, Rust suffers from a lot of the same problems as C++. Features like fast build times and debuggability actually matter there. It's not memory safety why game dev people are starting to get fed up with C++, it's the slow build times and feature creep of modern C++. In those areas, Rust looks even worse than C++.
I'm predicting we won't hit JavaScript levels of diversity (the problem space is just that much harder in gaming then in web) where the diversity itself is a hindrance but given the metrics of interest in rust and it's ease of use compared to C++ it's just a matter of time.
If I'm wrong the only think I think I would be wrong about is when this inflection point occurs. Either we hit in the future or we just passed it.