Let me try to clear the air of confusion here.
(i.e. no connection except that they share the first few characters)
Hence the language that we write these days in our .js files are nothing but ECMAScript codes. Most recently, ES5 is the widely used version and ES6 is specification is already frozen for implementation.
So logically, ES6 is supposed to overtake ES5. It was built for that reason. Though it would take a few months to be implemented fully by all browsers (Most modern browsers have already started shipping support for ES6 including IE!).
Comments? Let me know.