Well, in as much as crypto currencies are here to stay, I personally think that fiat currency is going to continue to exist for a very long time, and as long as fiat currencies still exist, then there will be need for banks to store them and deliver them to citizens when in need, also we should not forget that the value of cryptos is still drawn from fiat usd, every coins and tokens worth are still calculated using the US dollars, and until crypto becomes independent on the US dollars for its value, I think fiat will continue to play a big role in the crypto system and hence, will continue to exist as well as the banks.