Theres no chance for a digital currency in placing a fiat currency. We all know that fiat is being used by all people all over the world and it already established its name and its uses worldwide and for bitcoin no matter how it flies , it cant still place fiat currency , so this means banks would be still there because fiat do store on banks.
I agree with you, bitcoin and bank is two totally different concept, bitcoin's existence doesn't have anything to deal with banks and the fact that no matter how high bitcoin can grow or how low it can get, banks aren't affected by any of them. Therefore, bitcoin certainly can't replace banks, not to mention make them disappear.