I agree that we still need backends but I think they will need to move locations. The client app should sit on a dedicated server for serving static resources; Apache and Nginx do this very well. The new "backend" will just be your API endpoint. CORS will make this much easier but for now proxy pass will suffice.
In 2012 I see no reason why a JavaScript application should be served by anything but a dedicated web server.
Is this the endgame, apps split between client and server?.
I sincerely hope not, the current popularity for moving things client is just a band aid. The real problem is the network is not quick and redundant enough.
Ideally every node on the internet would be a server.
In 2012 I see no reason why a JavaScript application should be served by anything but a dedicated web server.