I honestly don't think you will see this feature. The demand for it is so low- how long has it been since an HDTV has been sold that does not accept all of the commonly used ATSC signals? Do even the low end CRTs lack this feature today?
Even if there was demand, you'd likely have bought a new HDTV before Dish would release such a feature. There are too many other items in the que ahead of it.
Tell this to everyone who rushed out to get a Playstation 3. There was such an uproar by RP CRT owners that they had to make a statement as soon as the news broke that all their 720p games would DOWNCONVERT to 480p rather than scale to 1080i. CRT owners were screwed, and they were angry.
I am one of them. I want the exact same feature described here, not just native passthrough, but the ability to select a resolution and then tell the receiver what to do with it. I think it is more "in demand" than you are thinking.