So I'm actually a big fan of writing apps in multiple languages, and I wholeheartedly support writing apps in higher-level languages that incorporate low-level components written in Rust. (This is, in fact, what Servo-based Web apps are!)
But I'm not sure I agree that there would be benefits in introducing a new language as opposed to just using an existing one. I think a Rust that used automatic memory management would effectively be a new language. There would be all the costs that come with introducing a new language: new tooling (even if based on Rust tooling, it'd have to be heavily modified), bootstrapping an ecosystem and community, and so forth. While making new languages is awesome, we have our hands full with the one we have :)
But I'm not sure I agree that there would be benefits in introducing a new language as opposed to just using an existing one. I think a Rust that used automatic memory management would effectively be a new language. There would be all the costs that come with introducing a new language: new tooling (even if based on Rust tooling, it'd have to be heavily modified), bootstrapping an ecosystem and community, and so forth. While making new languages is awesome, we have our hands full with the one we have :)