I don't think banks will disappear because of cryptocurrency because many are used to it their savings are on banks and some didn't even know about digital money. I think banks and crypto will coexist and it's better because people will have many options they can choose a centralized one which is bank and the decentralized one which is cryptocurrency.
The only condition of the banks to disappear is that when people will stop using Fiat and will only use crypto currencies. When people do not deposit money in the bank , the bank will have no source of income and they will have to be automatically closed.