Actually I'd rather not see the JS framework itself trying to solve this problem. The Rails asset pipeline (based on Sprockets) is an example of a good solution to this problem that is completely agnostic to your JS framework.

I'm serving a substantial Amber app this way and it works great. I'm taking it a step further by writing most of my code in Coffeescript, and I keep all my Handlebars templates in separate files as well. Sprockets just magically combines it all.