I still don't really understand the point. Why would you want this? Is this the answer to multiroom DVR or would the intention be to use it to sling from another device (HTPC or something?)?
If you had more then one Sling-enabled receiver in your home it kinda would be like a multi-room DVR. Remember ReplayTV? Back when I lived at my folks place, we had two of them in the house each attached to a receiver. Content recorded on one box could be watched on the other box and vice versa. It was awesome, it was sort of a way to have multiple tuners. As long as one of the ReplayTVs recorded a show, they could be watched on either one. And we didn't have to go to a website to start it, it was just a drop down menu in the UI.
People seem to think that DISH should just abandon using Sling and do something more like what DirecTV does with their whole-home DVR, but really that same experience could be replicated with the Sling tech. They just need to throw some engineers at it to get it working. It really no different than DLNA streaming it's just not using an open standard.