Banks won't disappear. Why? People will still need loans and a place to store their cryptocurrencies even if we switch completely from cash to them. Banks won't earn on transactions and withdraw fees like today. Instead, they will charge for exchanging cryptocurrencies and they will earn from loans like today they do. I wouldn't be suprised if there were more banks and exchanges in the future.
I do think that the reason why banks wouldn't disappear is because the government is backing them up. Plus, there will always be rich people that are too afraid to try something new. They feel safe with the government although obviously if a bank gets bankrupt, they wouldn't get their money at all.
"People need a place to store their cryptocurrencies", don't you own a wallet to not know that we already have that? If you are trying to emphasize security and all that, well that is all up to you. It's even less secure if you store it in a cryptocurrency bank (a bank that stores cryptocurrencies) because you don't know if their system was already hacked upon generating a private key for you. If you do it on your own, you know that you are safe if you generate it to a fresh computer, or a computer that has Linux as operating system, lots of measures can be done actually.
A place to loan isn't necessarily a bank. There are loaning services out there that aren't necessarily owned by the government nor the banks at all.