Well, you are assuming that so many cards are being graded that it will actually affect the number of raw cards out there in a significant way. This will not happen any time soon.
I’m assuming that it will affect the number of PSA 8-10 quality raw cards, yes. You can ask any person who’s been buying raw cards for several years and they’ll tell you just how precipitously the typical quality has dropped. I only purchase PSA 8s to open for my raw sets because of how poor the quality of raw cards is. If those PSA 8s weren’t slabbed, they would instead be on the market as raw. So grading has a clear and direct impact on the quality of raw cards on the market. Not the quality of the SP or MP or HP cards, but the quality of the raw NM cards without a doubt. And that was my premise in the first place: that more cards are being slabbed than need to be slabbed.
Keep in mind there is also a LOT less sealed product being opened. In the last few years, there was a ton of sealed WOTC product being opened which lead to a ton of mint cards being available. With no sealed product opened comes less mint cards available. I am not convinced that the small minority out there who actually grade cards affect the amount of mint cards on the market as much as sealed product being opened.
I agree that there’s less sealed product being opened, but most vintage cards are going to straight to PSA from the pack. So I don’t think that less sealed product being opened is the reason for the decline in the quality of raw cards. I think it’s more likely that the decline in quality is attributable to the million of cards that are submitted to PSA. A sizable portion of those aren’t 9-10 quality – and most cards graded under PSA 9 are not worthwhile to get slabbed. The direct effect of this is that it’s more affordable for me to just crack open PSA 8s for my binder sets than actually buy raw cards. If those cards weren’t graded in the first place, they would’ve been sold raw. So over 100 of the cards in my binders that were once PSA-graded were slabbed for pretty much no reason. So I do think that more cards are being slabbed than need to be, and that is has an actual effect on the raw NM card market.