They will make a new fiat or their own crypto because they cant afford bitcoin. Bitcoin are being hoarded by you and everybody else on this forum to get rich. As soon as there is a demand everyone will sell as high as possible and noone can buy.
You seem to not understand how markets and price discovery works.
When "no one can buy", the price ticks higher until there is an agreement
between buyers and sellers based on the volume needed to be traded.
From investopedia:
Suppose that a one-of-a-kind diamond is found in the remote countryside of Africa by a miner. An investor hears about the find, phones the miner and offers to buy the diamond for $1 million. The miner says she wants a day or two to think about it. In the interim, newspapers and other investors come forward and show their interest. With other investors apparently interested in the diamond, the miner holds out for $1.1 million and rejects the $1 million offer. Now suppose two more potential buyers make themselves known and submit bids for $1.2 million and $1.3 million dollars, respectively. The new asking price of that diamond is going to go up.
The following day, a miner in Asia uncovers 10 more diamonds exactly like the one found by the miner in Africa. As a result, both the price and demand for the African diamond will drop precipitously because of the sudden abundance of the once-rare diamond. This example - and the concept of supply and demand - can be applied to stocks as well.
The problem is that only a handfull of people have bitcoin. And of those handfull there are about 100 that have insane amounts. That would not sound good to normal people. And by normal i dont count those who see crypto as a salvation against the evil goverment but those who just want to live a normal life. I also think normal people would stick to the national currency and would not care if that was a crypto or fiat. Bitcoin is never going to be a national currency so that would be a party pooper.
Even if there is a demand for a replacement for fiat there is noone who would trade all they own for bitcoin when the price skyrocket. They would look for something widespread not something less used than Zynga chips. The rules for trade only works for trade. People dont want to trade currencies they want to buy bread and milk.