In a recent article its been described about the loss experienced by several banks just due to the increasing usage of bitcoin. For this banks have feared of bitcoin as well started to implement their own Blockchain technology based digital currency to keep them on the safe side. Possibly in future bitcoin gets circulated as the universal digital currency and every country will have their own digital currency.
to be honest that doesn't sound so plausible.
bitcoin is being used as an investment, which means people use banks to transfer money to exchanges in order to buy bitcoin (profit for banks) and then when they sell bitcoin they use banks again to transfer money to their bank accounts (another profit for banks). and all this time people are still using banks for all the other things like credit cards, loans, ... all profits for banks.
bitcoin can make banks lose money only if people start using it as a currency instead of using bank services which has not happened yet!