I'm confused. Are you proposing that web apps don't use URLs? If so, this seems pretty antithetical to the very nature of the web. One of the things that often aggravates people about web apps is that the back (and refresh) button is often broken because of a disregard for URLs. You can see Tom Dale give a defense of URLs here http://2013.jsconf.eu/speakers/tom-dale-stop-breaking-the-we....

As far as Ember Data goes, this is something that it's clear that a lot of people do indeed want. That said, you can use Ember perfectly well without Ember Data (see Discourse for example).

It's funny that you point to Rails as an example of consensus, because when you look at the server-side development community as a whole, there is certainly not consensus that the Rails way is correct. I wouldn't expect complete consensus on the client side any more than I would expect complete consensus on the server side. Rails (and others) have shown that you can have multiple healthy ecosystems each with their own points of consensus.