I think building ES6 support directly into the existing bundle is great as long as it can be done without conflict. As for timing, the time is now ... for instance I am using EmberJS for frontend development where everything is written in ES6 now and transpiled back to ES5 before being sent to the browser. BTW, I was a bit surprised to hear that you feel that TextMate developers don't use JavaScript much ... what is this based on? JS is one of the most used languages these days (I saw some metric recently saying it was the most used) and beyond scale it has momentum too with NodeJS and it's unique role in the browser. Not saying that your supposition about JS and TM is incorrect but I just find it surprising. Do you think JS developers are primarily using Atom? Sublime? If so, why do you suppose this is?