Higher interest rates could be the villain that cuts off the speculation. Another possibility is that too much dilution could exhaust the market. It's also possible that Y2K would start the big sell-off. In 1981 I went to an auction in New York to buy an antique duck decoy for my collection. That was a lot of money in those days and a record of sorts.
Collectibles are just like the stock market.
They have gone into orbit. Think of how much money that is. Picassos are plentiful and nine out of ten Americans don't care for them. There's just so much money around. Meanwhile, gold languishes.