I'm not sure it will happen in the near future, because many factors cause crypto difficulties to replace fiat money, including :
1. Still the limited amount of Bitcoin in comparison to the population, will Bitcoin increase the amount?
2. If this happens there is already government intervention or ruler over the existence of crypto, I think this will be a big problem as it is against the nature of the crypto world that does not involve a third party.
3. Even though we are in the modern era, I'm sure there are still many community groups who can not access the Internet, etc. Which is the main access to become part of the world of crypto.