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.
It's incredible how some people simply can't catch the whole picture.
You tell him that when 1 BTC will value 100000 $, people will still buy a part of it, it's not mandatory to buy ONE Bitcoin.
He still say that people will raise the price so high that no one can buy, because he still thinks people will want to buy ONE Bitcoin.
He can't accept that people will exchange what they can for the equivalent in Bitcoins, like 500 mBTC or 3420 uBTC in example.
And that all of that will be totally proportional to what can be bought with either BTC or $.
He just can't catch it.
If in the future there will be so much request for Bitcoins that 1 BTC will equal to 1 trillion $, then well yes, I'll set the bar to 1 trillion $ for my BTC, and whoever will want to buy, he will buy a fraction of that BTC.
If at that time 1 satoshi or 1$ will buy you a cappuccino, and you will want 50000$ in Bitcoins, then you will get from me 0.00050000 Bitcoins.
I will still sell you bitcoins, because there will still be some shops accepting $.
Then there will be less, and you will have to pay even more $ to have some Bitcoins.
And then there will be less shops accepting $.
And less. And I will still raise the price of my Bitcoins.
And at one point, AS I WROTE, the less gifted part of world population will still be sitting on a pile of $ or or £ etc. and the only use they will be able to do of those will be to warm up their houses by throwing them in the chimney.