I think that in the foreseeable future, the bitcoins will not be able to replace Fiat money, in my opinion, this is obvious. Many people are still financially illiterate, and cryptocurrency is an empty sound for them. Banks in their usual form will not disappear, but I think they will try to introduce cryptocurrency technologies and adapt them for their development. This should lead to a symbiosis of Fiat and the crypt or their parallel existence in banks.
Most likely it will be so.State-owned banks may not disappear,but private banks may disappear as unnecessary.When this happens it is difficult for me to predict,but it is likely that it will happen soon.(from 1 to 3 years)
Neither state nor commercial banks will disappear. For them, there is always work. It is unlikely that commercial structures will refuse to service in banks and will switch to the use of calculations in cryptocurrency. Banks issue the necessary documents for tax authorities and auditing. Cryptocurrency in this regard can not replace them. Also, banks perform a lot of specific functions for which cryptocurrency is not capable by nature.
Therefore, banks will continue to exist in its normal mode.