Javascript is a terrible language, even though Rust is experimental it would be a big improvement. And it does have attractive aspects as a language.
More broadly, breaking the iron grip Javascript has on client-side development would be wonderful and Mozilla is the last stumbling block in front of this goal.
Insofar as scripting languages go, Racket/Scheme would also be a nice addition. After all that is what Eich was going for when he created JavaScript. He wanted a language with scheme-like semantics but other forces wanted it to have a C-style syntax.
