bitcoin didn't reach there because all people don't use or want bitcoin payment method.So, currently jts impossible to disappear bank by bitcoin.We use bank for giving many kinds of fees etc by bank because store,shop don't accept bitcoin.so it's not possible for bitcoin to disappear e bank.
Banks would still exist even if Bitcoin was the biggest form of payment throughout the world, there are a ton of people who would still want to deposit their money in some kind of bank and not have to be completely responsible for everything they have either. While Bitcoin does let people be their own bank, there are definitely people who would just want to spend and move Bitcoin and not have to care for it.