Conspiracy theories. Why is it all these retro collectors on youtube are spreading the same narrative. Why has not a single person took the opposite stance? or everyone just follows the crowd these days? I don't believe any bubble will pop, and there's no reason why it should. They probably want people to sell off their collections so they can goyim them.
While I will not deny I'd love to see all games, retro and modern drop in price significantly for everyone due to decreased demand, I've seen enough in this hobby after being in it for nearly a decade (started collecting in 2008) that leads me to believe there is a bubble and it will burst eventually. Actually, it would be more accurate to say it will likely deflate gradually as I'm seeing now with many NES, SNES, and Genesis titles. Games like Punch Out, Metroid, and your standard fare must have titles have been showing up a lot more in my area and I've noticed that many of them are selling for slightly less then they were a year ago. Games like Wild Guns, EVO, and Little Samson are still ungodly expensive and will probably always be due to their rarity, but I can see them dipping in value over time.
Like I mentioned, I've also seen a lot of collectors, online and locally leave the hobby for many different reasons and because of that supply is returning to the market, meaning prices will go down. I also know many collectors that are still in the hobby, but they are no longer after the common and uncommon titles for specific consoles, meaning that it one less collector out of the market for a game like Super Mario 64 or Mario Kart.
And also, every collecting fad over the past 25 years has followed the same cycle; people in their mid-20s to early 40s get careers, have more disposable income and want a piece of their past, creating a market of collectibles. This exact same thing happened with vintage toys, comics, sports cards, Atari, and other items as well. Eventually as these people took on more responsibilities (kids, car payments, mortgage, ect) the time and money to indulge these hobbies diminished, leading collectors to leave their once beloved hobby, often selling what they had acquired. Eventually these hobbies became less and less popular until supply outpaced demand and prices dropped, sometimes significantly.
I do not know when precisely, but I expect at least classic Nintendo collecting to gradually burn out more and more over the next 5-year until games like Contra and Punch Out, hell, even games like Ninja Gaiden 3 go for at least 50% less than what they currently sell. Even games like Little Samson I can see dropping to around $500 by this time. Some might see this as a bold prediction, but as stated above, we've seen these collecting fads before and we all know how they end.