I have been looking at React (will probably skip due to the patent license) and Vue, but cannot imagine going back to semicolons and (excessive) curly braces and parens.
If you married CoffeeScript just out of convenience (being able to avoid prototypes, bind, etc.), then it no longer serves much of a purpose. But if, like me, you fell in love with CoffeeScript's beauty, then no amount of ES6+ features will make it obsolete (as long as you can also keep using those features directly in CoffeeScript).