I don't know that there is much question of replacing Rust when it isn't in use except as an unstable experiment with a lot of interest. You could replace Rust with outright vaporware.
At worst, it says that Rust's toehold is tenuous enough that even vaporware could replace it. I don't agree with that, but I can understand the sentiment. Think "knocked back with a feather".
Rust isn't stable. It really hasn't seen any serious use.
Even the Rust home page itself currently states, "Rust is a work-in-progress and may do anything it likes up to and including eating your laundry."