The trend I see is that the "extra-native" features that these DSL style frameworks were adding are now being taken care of by compile-to-js languages (CoffeeScript, ClojureScript). The question is whether this is advantageous. Certainly it removes a big dependency on the client side but this is at the expense of an extra mental leap during development. I think we'll start seeing big advantages when the debuggers work properly (http://www.meetup.com/Coffee-Script-New-York/events/41391392...).
I had a conversation with jashkenas about this - I don't think source-mapping alone will ever be enough. For the debugging experience to be ideal you'll want things like locals inspection as well being able to evaluate expressions during the debugging session. Perhaps tools that into WebKit's remote debugging protocol can get us closer, http://trac.webkit.org/browser/trunk/Source/WebCore/inspecto...
