Fundamentally, banks are in the business of pricing (credit) risk. This can continue in the Bitcoin world too. Banks can still make money by lending.
It is only recently that banks have started focussing on fee income (maintenance fees, transaction fees, etc) because it carries no risk. They have always been in the business of lending and collecting interest.
I do agree that Bitcoin and banks can be "friends", if not friends, coexist. I dont think Bitcoin will effectively replace national currencies, but both systems will coexists and create a sort of balance (ying-yang sort of stuff), a system that is deflationary and a system that is inflationary that can interact with each other.