RPC's over WebSockets is what will replace REST/Ajax.

On the client-side you have code like this:

  clientapp.sendRPC.doSomething(123);

And on the server you write code to receive it:

  serverapp.receiveRPC.doSomething = function(number) {
    write(number)
  };

No Ajax, no URLs, no REST-ful religion. In fact ajax just feels wrong now. I unfortunately have to add some backward compatibility to my websocket apps, and I just get this really icky feeling like I really shouldn't be doing this arcane stuff anymore.