And even now I get the feeling that Django is 
     steadily being edged out by Rails.

As someone who is pretty familiar with Django's internals I can say that I don't really care -- because I can always modify Django to suit my own needs and indeed have done so to work around certain problems it has.

     3 or 4 years ago you wouldn't have looked a bit crazy
     for picking either over jQuery.

Making choices is also a matter of taste. I picked jQuery because it was lighter / easier to use ... but right now, honestly I'm searching for something else, because jQuery is starting to look like those alternatives I avoided (too big). Also, you pick something based on real constraints, not popularity - does the framework do what you want? Is it too light? Is it too heavy? Does it have third-party contributions for doing X or Y? And so on.

     What about coffeescript? Is it here to stay?

Does it really matter? All that matters to me is that with CoffeeScript I can avoid cross-browser syntax differences (dealing with IExplorer syntax issues is a pain in the ass). It also makes my code prettier. It makes me happy. When CoffeeScript will be gone, in the worst case scenario I'll write a script to convert from it to the latest fad du-jour.

This highlights an important point however - because Javascript is a standard that is here to stay, with CoffeeScript I'll have a clear migration path. With anything on top of Flash however, you don't.