Bitcoins cannot make banks disappear. But it will considerably decrease the amount of people using banks. In future, even a situation could arise in which banks could only be used for getting loans and no transactions done through banks.
Indeed. Digital currencies are still pretty new to people and I doubt that bank will disappear in the next few year. Bitcoin and other crytos need to do a lot of things to be adopted and recognized by people and this process may take at least 20 years. If this process every finished, banks would disappear in about 30 years after the adoption