What you describe represents a very small percentage of current assignments. Yes, that percentage will increase as more and more typical 1004 assignments get downsized to waivers and PDRs, but that large decrease in supply of work will be large compared to the decrease in the # of appraisers. Appraisal supply will go way down, where appraiser supply will go some down.
I really think the meeting point of this supply/demand curve will still force prices down for every available type of assignment. I fully expect that to bleed over into commercial work as well, because when CG's do a significant amount of residential work. When that dries up, they will be forced to compete more heavily for commercial work. They may prefer residential, but it will be that, or hang up the disto.
We are already seeing these price movements, I see no reason for the trend to change, especially with the imminent on-boarding of the PAREA hordes, which will INCREASE the supply of appraisers at the worst time possible.