It will... - make it easier to use multiple processors - use a new type of DOM designed for web app GUIs which can be translated as necessary back to our current DOM - have built in version checking for its interpreter/JIT - make it easier to manage memory usage - have a module system - be highly specialized towards the web and web app development - eg. built in language components that make communicating with the web server easier - be messy - people will be trying to fix everything anyone thinks is difficult/wrong about Javascript and modern web development - be easier to implement in the browser

For the immediate future, I see Mozilla sticking with ECMAScript and Google sticking with Dart and trying to make it like the language defined above. Google will likely eventually build Dart into normal Chromium and Chrome and build a plugin for Firefox, which nobody will use. Others will build a Dart VM using asm.js to make Dart work efficiently within Firefox. Any successful new browser languages will be able to compile back down to Javascript, although after a while they will be buggy as the Javascript stops getting as much maintenance.