I don't think Bitcoin can replace FIAT money for various reasons. The first reason is the ignorance of Bitcoin by a large part of the population, although lately more can be seen on TV and other media due to its new ATH. The second reason is the age of the world population, as a very simple example there are people (the oldest) who still do not know how to send an SMS, I cannot imagine those people opening Electrum and encrypting private keys. The third reason is the one we know best, banks (although more are being added lately), governments and other institutions that do not allow the state to change.
Those are just some of the reasons many people would not replace their FIAT for Bitcoin, especially out of fear of the unknown and digital ignorance.