I don't think that it will disappear banks as banks are already have much works to do and their work is not only to store money for people but they are also maintaining the financial affairs for governments and for different organizations.
The bank's tie with the government is the one that keeps it surviving and not just the money... That is why it will be difficult for bitcoin to make banks disappear, bitcoin could only substitute the money but not the other transactions that banks are holding...
Surely it will be hard for bitcoin to make the disappearance of banks in the scene. And you are right with it because of sovereign power of banks that they are connected and being controlled by the government. But it depends to the banks if they will allow bitcoins to enter the scene or make an adoption for the usage and services of bitcoin.
We should always remember that bitcoin is just an alternative for using fiat money online. There are people that doesn't prefer bitcoin as a form of online transaction and thus banks will always be there. This is also the same with bitcoins, there are people that prefers using bitcoin to some of their online transactions and thus they will only need bitcoin wallets however, they still have their bank accounts for other transactions that most need it.