It depends on whether or not the entire thing falls apart, because registry contestants no longer believe in high grade slabs OR give up on the collecting concept.
If people continually get scammed as they are, do they pull out of their collections and start selling off in quantity? Or do they continue to fill the gaps in their sets with the only remaining high grade cards on the market? It's kind of like this:
Take the 1948 Leaf (baseball, football, boxing) sets, which have been found to be completely inaccurate. If one person who had 10 altered high value cards out of the complete set of 100, are they going to feel enough animosity to PSA to sell their 90 "good" cards or are they going to buy back the 10 cards they now need? How do they (or the market) trust their own "good" cards? What if it's 15 altered or 20 altered out of 100? Each collector will have their own breaking point.
I have seen a bunch of collectors post something to the effect of: "Man, I hope these cards all lose their value because I'll be right there with my cash to buy them on the downswing!" But is that just talk? Are they willing to buy into a recession downswing?