Banks are not going anywhere even if bitcoin gets on the mainstream there will be many people who will prefer to use banks and save their money in it as they feel that banks are the most safest place to save their money which is actually true.
It is a sure thing because banks are being endorsed and trusted by the government. They are the one who controls the market of banks that's why people and will be manipulated by the media which is controlled by the government too. Because they can just simply boycott services from bitcoin and tell the people to stay with the banks.