Yes that is right, and i agree. For now and in near future people will need banks for exchanging bitcoin to fiat currency, and i guess nothing more. Because of fluctuation who sane would take credit from bank in bitcoin 
. But why i say in near future, well we all know how bitcoin works, and for paying and dealing with bitcoin in day to day life we do not need banks. But still, some people will need banks for safe keeping their bitcoins.
. But why i say in near future, well we all know how bitcoin works, and for paying and dealing with bitcoin in day to day life we do not need banks. But still, some people will need banks for safe keeping their bitcoins. In fact, it makes perfect sense to take a Bitcoin loan from a bank
It is the bank who is to suffer most from Bitcoin volatility, not the borrower. For example, if you take 1,000 bitcoins and then sell half of this amount for dollars. Let's assume that Bitcoin rises a few times after that. Now you can safely default on your loan (I don't say that you should since I just follow the logic of the bank), forfeit your collateral (whatever it might be), and then buy what you forfeited with now expensive bitcoins and still have some bitcoins left in your pockets (plus dollars that you sold half of your bitcoins for). If Bitcoin goes down dramatically, it's not a big deal either. You just buy back the inexpensive coins with the dollars and return them to the bank (plus any interest accrued)
Yes we have both advantage and disadvantage for this method. According to you if the price drops it is an advantage for us to buy more coins and return to the bank. If the price increase then it is an advantage for banks they will get more income. The only solution for this problem is first the bitcoin price will be stable at one rate like our fiat currency. Once it's done, then we can do this business or else it is impossible.