In my opinion, things are not so simple as they look like in the form of theory. There are millions of banks around the world and the US federal bank is one of the powerful one which work to maximize the profit and at times of need, assist the government. A cryptocurrency concept will not be so strong to disrupt the banking system though the small banks do fear the system.

I do agree that banks must adapt technologies but do not think for a while that they cannot survive without the cryptocurrency. The banking network is very strong and this cannot be out kicked so easily.