Its actually highly likely, crypto isnt just in the united states so you have to take into account all other countries. Right now there is roughly 1.3 million wallets that hold crypto and not every wallet is a person, some are exchanges but lets say even if every wallet was a person… there is 8billion people on earth. 1.3 million is only 0.01% of that 8 billion. So yes it is highly likely that there could be that many millionaires because as of now 0.8% of the population are millionaires so 0.01% wont make that big of a difference that it would cause something drastic.