Yes and no. Although we get some fantastic features, one of the most critical- the ability to neglect parens and curly braces- is lost in es6. I'm working on an es6 project right now and still prefer coffeescript.
That's interesting - personally I've always really disliked that about Coffeescript. It may just be because of how familair I am with C-family languages, but I always liked the default Javascript style far better.
So from my perspective ES6 is the best of both worlds - the better syntax of Javascript and the features that Coffeescript gave you.
For functions of single arguments, you parameter list parens are optional.
But it's not an objective fact that coffeescript's syntax is better. I prefer ES6. And even if you prefer coffeescript, it seems strange to claim that the most critical feature is purely aesthetic.
Assuming it's all ultimately JS, the aesthetic side is a big deal. It results in an easier time understanding and being able to debug the code, which is a huge, perhaps underestimated win.
So from my perspective ES6 is the best of both worlds - the better syntax of Javascript and the features that Coffeescript gave you.