I've already felt the slowdown in changes. I did have a (little) break from Rust and the only things that have changed are ergonomic improvements and the async stuff. This is a predictable outcome given the roadmap for this year was one of stability for the language.

When async/await stabilises, I think it's going to be less about the language changing and more about the ecosystem. I think there is going to be a lot of development on top of async over the next few years and we're going to learn a lot about the right way to structure programs and deliver useful abstractions. This is going to be particularly true in the embedded space I care the most about.

This is the hidden downside of having a good package manager - knowing how to use the ecosystem is as much of a skill in real world programming as knowing how to use the language. To be clear though - that cost is entirely worth it.