REST is just a layer of indirection over a regular RPC backend anyway. It may be easier to reason about things like caching and side-effects on the HTTP level. Of course HATEOS is mostly useless, unless you can stay within the general purpose protocols, like AtomPub and extensions.

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

If SPDY takes off, there’s hardly any advantage to WS besides push events. Stateless protocols are easier to scale.