I think that the focus now should be allowing other more modern languages in the browser by means of Web Assembly. Rust is a great candidate for dealing with immutability and unsoundness concerns. I can't wait for wasm to be fleshed out more.
It does beg the question though, would web development be as ubiquitous and as popular if the core language in was statically typed? Does the freedom JS offer you allow greater adoption overall, meaning that it's beneficial to loosen the type restriction as the ecosystem will flourish because of it?