this will never happen, money are way too important in terms of politics, economy and lifestyle.. crypto might become a side currencies but there is no way crypto will replace money in the next century
But crypto is a form of money, isn't it? Are you aware the fact that most circulated supply of money is not cash (3-5%)?
Governments would actually prefer all money exchanges to have a digital footprint, so imo it's not that far away from us.