ES6 is groovy. Many features are in the runtime and not the syntax, and just work as-is. As other syntaxful features start to come into existence and then universal implementation in most active browsers, CoffeeScript should begin offering them -- at least the ones that align with the mission statement.
Some will be troublesome because of intentional syntax conflicts, like "for of" and perhaps classes. It'll just take a bit of design work to make things copacetic.
That said, in the long run, the future is going to be JavaScript (if it continues to evolve) and languages that are much more radical than CoffeeScript. For more thoughts on that, see: https://www.youtube.com/watch?v=DspYurD75Ns&t=36m57s
How do you envision the future ? Everything expressed as a js descendant ? no more syntactic distinctions ?
I just feel like it's half the work coding, than with JavaScript.
If they get the ES6 import/export done, I got all I need.
With that stated, I still overwhelmingly prefer CoffeeScript's syntax to ES6. I'm glad ES6 took some inspiration from CoffeeScript, and Babel is a great way to bridge the future of JavaScript over to client's of the present, but I'll always prefer the CoffeeScript syntax for white-space sensitivity, support for optional semi-colons, optional parenthesis for function calls and optional curly braces for object literals. I don't need those features but I really like them. For me, the real future of JavaScript is a re-imagined CoffeeScript that takes on some refined semantics in order to bring ES6 feature support into the CoffeeScript compiler. Admittedly, that is not a simple undertaking (though I'd imagine the code would be simpler as a whole since it would necessarily trash obsolete features like pseudo-classes etc), but I know I'm not the only person who would love something like this.
I don't know how jashkenas is feeling about ES6, but one day I'll have my ES6Coffee, even if I have to brew it myself.