[higherpurpose]

Will Spidermonkey be rewritten in Rust eventually?

Sidenote: WebGL 2.0 should come with ASTC support to be relatively future-proof.

[gsnedders]

Note that JITing compilers gain a lot less from Rust's safety guarantees than most code: you can easily JIT some code that breaks one of the safety properties that Rust ordinarily defends.

[steveklabnik]

That is too far in the future to see.