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.
Neither fiat currency nor banks are going anywhere as majority of the population across the globe are dependent on it and using it since its inception and in that scenario its really hard to believe that it will get replaced with bitcoins as at this stage there are very few people who are aware about bitcoins.