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.
it's true maybe the bank features will change due to popularity of bitcoins in the future but the bank will not dissapear because it has many benefits not only putting money to your bank.