The only issue I foresee is tools being built around the use of ES6 that compel you to abandon it.
I've learned that less is better. I don't use JQuery, I don't use Lodash. I don't use React, I don't use ImmutableJs, I don't use Webpack or CommonJS. All of these tools are more a burden that a blessing and you just end up stacking on 100 dependieces asking "Is this really better?"
I learned this lesson with Cucumber/RSpec/Caybara and etc.. I started asking why I had to use these over plain old TDD and so I used TDD for a month and I found out everything was totally fine.
I don't even really use Arel in ActiveRecord. I just write raw SQL that serves JSON directly back. I made it easier for me to organize SQL in partials just like views and to injects variables and conditions into my SQL.
I went to great lengths to evaluate all these tools because as a work-form home contractor I can afford the time, and the "what if" really bothers me.
I still working in Rails with Sprockets and CS and I write all my SQL by hand.
Less is Better.
All these kids want to do a bunch of busy work and for no good reason. It makes the feel productive.
I have tried dropping CS but the difference in productive was too great to drop. Its not that I'm married to CS its that it does what it says. It makes your JS concise so you can be more productive.
I felt AngularJS dying and so I spent 3 months researching React and building client apps in React. I just didn't get all the work extra work and settled on Mithril.
The hardest thing was giving up writing HTML-like templates like I did in AngularJS but I remember that was my first aversion to AngularJS where I swallowed the medicine. I had to swallow more medicine to unlearn that. Mithril paird with CoffeScript makes writing markup in CS a joy. If I had to do that in regular JS I could see why people would be compelled to use ugly JSX.