Tl;dr at the end.
Some cards will retrace, some will continue to rise.
I don’t think anyone can really predict what most cards will do, other than through feelings, which isn’t data. The only thing I can compare this to is 2017, when I re-entered the hobby. At that time many cards peaked like for example some 1st edition base PSA 10 non-holos were up to $500-800, and by late 2017 early 2018 had can come back to as low as sub-$200 very quickly. Other WOTCs had similar retraces.
The differences I see are that back then you had a significantly larger number of sealed packs and boxes being opened because the expected value was still high enough to make it worth it. Especially before the prices dropped. You had people break boxes and send piles of cards through PSA to take advantage of the meteoric rise in prices. Mind you, many 1st edition WOTC boxes were around or under $1000 dollars at the time. The other supply factor was flipping. As prices were increasing, people were buying cards in hopes they could sell it a month later expecting the price to go up. When prices dropped, you had flippers dumping product to cut losses in addition to the extra product from burn and churn entities breaking sealed product.
From 2018 until the end of 2019, prices didn’t change much for a lot of cards. Over that time the purchases of that large supply was slowly done organically by interested collectors and flippers had mostly peaced out because there was no incentive as prices weren’t climbing. Along this timeline, box prices had continued to rise.
2020 hits, and even before quarantine we started to see a natural climb in prices because fewer boxes were being broken. Most of the excess supply that was hanging on the markets went to genuine collections. I think another factor is when you consider how closed in the hobby has been for so long. Within the last couple years especially, Pokémon has finally started to seep into other hobbies like sports, mtg, youtubers, and many other facets of our culture, increasing exposure and thereby demand. Put on top of this the continued increase in consumer income for people who like Pokémon through better paying jobs. When $100 used to seem like a lot for a card, suddenly for a lot of people $1000 isn’t such a big deal.
After considering all of this, then factor in 2020 with quarantine, stimulus checks etc. These 2020 factors are like a gust of wind under our sails, but this ship has already been sailing steady for awhile.
Tl;dr: Demand has continued to increase the past couple years, both from within the hobby and new interest from outside the hobby, while the sources of supply have dwindled since it’s more valuable to keep sealed product sealed. To say that demand will dry up well before supply does makes no sense to me.