It won't. We are still far from massive adoption. We are just starting. And it's not enough to replace fiat currency. And even if cryptocurrency receive mass adoption, fiat will still remain because of the government. It's what they can control so they wouldn't let fiat to ceased and be replaced by cryptocurrency. Instead of thinking that crypto will replace fiat, I'd rather go for both of them being used in the future. They can co-work together in the economy. But it's still up to the government if they will let crypto be accepted in their country.