JavaScript is no longer the only language. I wouldn't be surprised if JavaScript is used at all for large projects in the future. With things like Dart, TypeScript, CoffeeScript, and asm.js JavaScript is becoming more of a compile target.
This is actually a scary prospect, considering how consistent JS is as a language, let alone as a bytecode replacement.
I expect that to happen sooner rather than later, it is not an impossible problem, and it is far preferable to trying to use JS as a compile target.