Banks would not disappear. Maybe the way banking works might become different, but even that is a remote possibility.
What you need to remember is that banking is big business. If bitcoin were to cause the banking industry problems, the banks would fight against bitcoin. And they would wage that war through government; By using legislation to keep bitcoin from causing problems to their industry. And government would happily play along.
Yes, i agree!banks would definitely would not dissapear as long as the fiat did not dissapear. It is impossible to loss bank. Banks have an important role in the world. Although the born of digital currency do not need bank, still the world needs bank to control fiat. The bank can manipulate fiat and fiat needs control. Maybe a few changes from bank may happen as the digital currency enters but not to the point that we will loss bank.