It's too simplistic to believe that banks are going to collapse anytime soon, that's not the case. They're adapting and implementing bitcoin within their old legacy system: they basically tapped into our world and now they're leveraging it to streamline their revenue models. Don't you see it?
I agree that, those that will not adapt, will eventually fade away and collapse.
Banks don't even need to adapt too much. The banking system is under the protection of states and therefore states will regulate social relations in such a way that banks will exist as long as the states themselves exist.
If it is profitable for banks to use cryptocurrency, they will do so.