While no one can foretell what will happen. Based on supply and demand. Prices should go well below MSRP for a while. The market would be flooded with used GPU. Who'd pay MSRP for a new GPU. If the same model less than a year old is going for less than half. Sure some still would but retailers would end up getting stuck with a big surplus. As would everyone else in the supply chain. Even lower end GPU would have to go down. Who'd buy a new GTX 1030 if they could get a like new GTX 1060 6GB for about the same price?
I'd also expect nVidia and AMD share prices and profits to take a hit. Right now they can't manufacture GPU fast enough. Suddenly they'd have a surplus sitting around. They might have to sell them below cost to clear out the inventory.
I'd imagine the same would hold true for PSU. The market would be flooded with 1200+W Tier 1 PSU. All PSU prices would have to go down.
The question is how many GPU are being used exclusively for mining right now? ie Multi-GPU mining rigs way beyond some gamer just paying off an SLI/Crossfire setup. How far would prices go if say 25,000 were posted at auction on eBay per day.