Bitcoin will be like gold. people will buy it for its value not necessarily for payment methods like fiat. I think the intention of the questions is really "When crypto will be mainstreamed as a payment method".
About a month ago I was also thinking that when people see that Bitcoin will be accepted worldwide, they will look for it like gold, but it will be more difficult to obtain it because if there is a lot of demand, the price will go through the roof, it will be like the best savings of people's lives, then as a payment method it will be the ideal but it will be as valuable as gold.
The human being behaves erratically most of the time, when the BTC drops in price, when it was at $36k people didn't buy much, but I'm sure that if these days the btc reaches $100k people would buy like crazy, I think that from here is the reason for my thoughts.