The usual national currencies of various states will exist as long as these states exist. However, the form of these currencies may vary. Therefore, it is possible that in the very distant future, the paper money of the states may disappear and will be replaced by their other types. However, they can not be replaced by cryptocurrency, because cryptocurrency will never become national money.
At the same time, in the near future, paper money of states can gradually disappear only in the most highly developed countries with a very high level of income of the population.