The subtext of this article is that underneath all this glitzy new syntax, class mixins are absolutely nothing new. The semantics are the same. The important thing is to focus on the underlying principles and let the syntax evolve as it wishes.
dude, es6 is way too mainstream for cutting edge web programming. If you're not using es7 already you might as well still be using table layouts
I've started writing my own ES9 specification to get a jump on the really cutting-edge stuff, it's influenced by functional languages but only ironically.
Don't stress, while ES7 is exciting (and I'm using parts of it, async/await alone are worth using) a fair bit of it is still up in the air. Unless there are particular features you'd like (for myself that is async/await and decorators), es6 alone is well worth it.
Don't get worked up over this. Let the dust settle and the smoke clear. Take a deep breath and relax. You'll need it in the JS community.