Everything is possible in this life. However, people need their own place of anonymity. Every person sometimes buys a thing (service), which he does not want to advertise. While electronic money will not provide at least some privacy, fiat money will remain popular among ordinary people.
Cash is not to become extinct after cryptocurrency revolution. Cash will stay there forever but there will be many additional payment methods in addition to cash with the development of new platforms.
This is like a technological development, remember old days people were using gold and silver for shopping.