> Knowing exactly which of these options CoffeeScript will take
> will give me a better understanding of the long-term viability
> of CoffeeScript.
So in general, what I'd like to see mainline CoffeeScript do, is adopt useful ES6, ES7, and ES8 features, as soon as they land in enough platforms/browsers to be widely useful (yield may be at this point already, or very soon), and to continue to try and find a pleasing minimalist syntax for writing and reading them. If this means taking the ES* syntax wholesale, that's fine. If it means minting a new (and hopefully, but arguably, nicer) syntax, that's fine too. And if it means breaking backwards compatibility, that's also alright, as the compiled lowest-common-denominator JS output will still be perfectly compatible with the new stuff.