Lots of good replies from everyone here, and plenty of things I agree with. I will just comment on two things that I find interesting. I could be wildly wrong and acknowledge it! Feel free to disagree.
Regarding the Lv. X dumping on marketplaces like Alt, I’d be very willing to believe there is an element of pumping to it. As others mentioned they are not even the rarest cards in their own sets and some sales seem exuberant. Few of these sales are on eBay. Does that market collapse maybe 5 or 10x once these bros move on and someone is left holding the bag? Sure I can see it!
Whatever the origin of this insane wave, the practical effect has been to incite and inflate most of the mid era market (I refer to RS and DP era mostly for the below analysis).
All boats rise with the tide, as others here have pointed out. I have cards like reverse holo Pikachu Holon Phantoms PSA 9, that were not even $100 before the current boom, now pushing $7k in auction. I could see at least some of this being sticky even in a few years, owing to collectors fundamentally shifting to realizing value and rarity of these cards, many of which have pops that are not much higher than WotC era.
It is also possible for people’s tastes to fundamentally change over time. Legendary Collection was reviled for years before being worshipped today. I sold ex era reverses for $5-7 in my binder at card shows for years but I doubt that time will return. (I think DP and BW are next on this list btw).
The crypto and sneaker bros referenced in this thread correctly deduced that for anything with small supply, pushing the demand lever even a bit can cause wild price inflation. Even if they go away, I think it’s possible that just by drawing people’s attention to these cards, they will fundamentally change the bottom price of this market. We’ve seen this several times since 2019, first with wotc vintage, then subsequent sets.
Where will this go in a few years? We’re in wild mass guess territory. I think that there’s a nonzero risk of market collapse, owing mostly to macro factors like AI speculation bubble burst, stock market slowdown, PSA experiencing some huge crisis of confidence etc. Personally I am very skeptical that 100 or even 90% of the huge mass of people interested in Pokemon now will still be so in 10 years. But even for the ones that are left, I still don’t think we’ll get to $80 PSA 9 reverse holon phantoms Pikachu again. Sorry for the long ramble, that’s my thoughts so far 