I think it's possible theoretically only. People are not ready to stop using banks. Peer-to-peer system is like something mythical to them.
It is possible for Bitcoin to take over a bank but to be honestly think that the change of that happening are almost at zero.
The chance us bigger that Bitcoin would be taken over by a bank.
You are wrong as bank do not work only to save and transact our money , only in some duties bitcoin will replace banks while in all other duties which bans have will remain with banks and for that banks will survive.
yeah, banks sometimes provide really good and required services and i doubt that bitcoins will ever make banks disappear