It means pigs will fly before Firefox supports alternative languages like Dart or Typescript, since JavaScript is his baby. I'd be surprised if asm.js even continues to be supported, he's argued so strenuously against the idea of javascript as assembly, even though there are now almost 100 other languages that compile to javascript: https://github.com/jashkenas/coffee-script/wiki/List-of-lang... and Google, Microsoft, and Facebook (hack) are all sticking to languages that use types.