I mean, I do see upper-end collectors selling pins in order to pay for the new hot game. I picked up my EHoH for $7k with art blades, a shaker, and <100 plays. Guess what game the seller was getting ready to pay for? Yep, the new Avengers. And why did he do that? Because he was hyped for the new hot pin, and he needed the money/space.
I think an upper-end game like GNR will lower prices, but only for other upper-end games. I would imagine a lot of DI's, Wonkas, WOZ's, Turtles Prem/LE's, and B/W Classics & Remakes will continue to show up on the marketplace for well-below MSRP prices. But like many others have said, I would expect used older and lower-tier pins to continue to rise.
Because owners with a lower budget still need something to buy, and NIB pins are too much money for a lot of pinball enthusiasts. Plus, replacement parts/components for older games are more plentiful than ever, so that helps keep the old games going strong.