If Tokio was the final answer, https://github.com/tokio-rs/tokio-uring/ wouldn't exist.
While Mio will probably not implement uring in its current design, there's https://github.com/tokio-rs/tokio-uring if you want to use io_uring in Rust.
It's still in development, but the Tokio team seems intent on getting good io_uring support at least!
As the README states, the Rust implementation requires a kernel newer than the one that shipped with Ubuntu 20.04 so I think it'll be a while before we'll see significant development among major libraries.
Tokio supports io_uring (https://github.com/tokio-rs/tokio-uring), so perhaps when it's mature and battle-tested, it'd be easier to transition to it if Cloudflare aren't using it already.
Have any other Rust async runtimes use io_uring/gotten at all good yet?
Best of the best modern systems programmers gotta get good sometime. Not sure if it's happening yet. Ok here's one point of call: https://github.com/tokio-rs/tokio-uring