There are 63M millionaires in the world.
There are 1.26M BTC left to be mined.
That's 0.02 BTC for each millionaire.
Discussion
There are still 21M BTC, people will sell, but still there are less BTC than millionaires. Number of BTC will remain 21M and number of millionaires will go up.
Don’t forget people loses their keys through time, another will die and take the key with them.
What will really trigger your nut is that the more millionaires will buy BTC, the more bitcoiners will become millionaire, until USD will worth so much less that millionaires in USD will no more have any value, we will talk about wholecoiner or maybe millionaire in sats or just bitcoiners, as the new "your are rich" standard.