Currently, when you need to borrow money, your banker just edits your balance account and create money magically. You then pay back monthly.
Banks won't be able to do that with Bitcoin with its limited supply. You can't print bitcoins.
well then they have to go back to the "honest banking" system instead.
which means you lend what you have instead of lending more than you can afford. and they will lend actual money (in this case bitcoin) instead of credit. and having limited supply is not a problem! imagine if price was 1 million and you wanted to loan $100k you simply take 0.1
BTC!
but also there is another rout they could take, which is probably what they will too. and that is the same methods of using "credit" instead of actual money. for example when you loan money to buy a house you take a check and pay the check to other person and that other person deposits that in his bank so there is no need for real money to change hand but only numbers in their databases!