yes that is right that bitcoin can replace banks but the banks cannot be disappeared by the bitcoin network because the banks are the most reliable place to deposit your money not bitcoin. in that bitcoin network your money is not secure because of bugs and fake members and especially the hackers. your account can hacked or money could be lost if password is lost or acount could be deleted. but if banks lose your money it is responsible to give you your money.
in bitcoin you can not retrieve your money.
Yes banks holds the responsibility of its users in case anything wrong goes with their savings and if its bank's fault they will help in recovering your money, and that is not possible with bitcoin.
I doubt that it will be happen no program or sytem can replace banks but it still exist due to law of government implemented to it and i think bitcoin cant never ever make bank dissapear because bitcoin relay On banks si it can be exchange and be used without bank bitcoin is nothing and thats very impossible idea for bitcoins state.