As more and more people write software in languages that compile to JavaScript instead of directly hand-writing JavaScript the demand for JavaScript becoming a better compile target grows.
In that sense adoption of Dart, ClojureScript, TypeScript, Elm et all will continue to accelerate JavaScript (language and runtime) improvements.
All part of the plan. I've been saying this since 2012, Dave Herman and Alon Zakai of Mozilla Research (asm.js creators along with Luke Wagner) said it before me:
In that sense adoption of Dart, ClojureScript, TypeScript, Elm et all will continue to accelerate JavaScript (language and runtime) improvements.