I found this expression on the news channel about the crypto currency: "Anyone who will try to buy coffee for cash in 2023, runs the risk of causing laughter from the seller, that he does not use crypto currency."
how do you think, is it realistic? Can a crypto currency replace national money?
I think that it's possible, but it will take more time.
Definitely not in 2023, that's a few years from now and that is too early to happen. Most of the government in the world has no concrete policy about cryptocurrency and it's not even their priority as well. If any in the first world countries would initiate to change the status quo then it is possible to happen but seeing the current situation now, no single government in the world today wants to change their own currency to a highly volatile cryptocurrency.