Just from talking to people out riding this summer it seems like a lot of people bought bikes they could technically afford but were way above their preferred price range simply due to availability.
What people wanted was $500 bikes but there were only $2500 bikes so that's what they got. It's not like they're stupid or even necessarily made a bad choice. They wanted a bike and got the bike they could get.
Not being able to dine out, take vacations, or go to concerts has put a lot of disposable income in the hands of a good chunk of the population this year.
Some of those people are probably on bikes that don't fit that great due to availability and they'll be looking for better sizing as they get more into it.
And of course the majority probably won't get super into cycling but again they weren't going to either way so it's not really a "lost" sale.
Plus I mean it's kind of a running joke among bike people that you don't really upgrade like it's a piece of technology. You keep the old ones and just accumulate more as you go.
Once the market stabilizes the bike manufacturers and dealers will go back to offering generous trade-in and 'last years model' discounts and those impulse bikes will have to drop a lot off their original price to look like a bargain. I suspect it will look a lot like the US used car market where a new car is cheaper than the same thing with 20k miles - by the time you account for manufacturer promotional discounts and dealer haggling.
Also I'm not sure I'd want to roll the dice on any used carbon frameset or wheels. Are modern carbon frames less brittle than I am led to believe?
Also it's the winter right now-- a historically low biking season. Your friends might pick it up again in the spring.