Pentax has never released a firmware update that brought features from a newer camera into an older camera. In fact, they have seldom released firmware updates for cameras that are no longer in production. A notable exception to that is the recent update for the K10D, but that was a minor bug-fix, having to do with certain SD memory cards.
I think that the only firmware update that Pentax would release for the K-x at this point, is if they introduced a new flash system that required it. By updating older cameras, they might sell a few more flash units. What you're suggesting, moving features from the K-r into the K-x would have the opposite effect: it would reduce the reason for someone to buy a new camera, and might impact K-r sales. Why would they want to do that?
But then, I've been wrong before.