Certain things will remain unchanged no matter the circumstances so regardless of crypto existence and adoption it's definitely will be an impossibility for banks to go on extinction. For instance we need light and thus since the use of the internet isn't adopted, we expect electricity to go on extinction?? Hell now it's never gonna happen. I think alot of patience is needed so the banks can see the advantage and benefits of cryptocurrency and enhance it's adoption.
Half of the banks worldwide at operated by government which means if Banks goes into extinction, that means the government doesn't exist again which is not possible. The government might decide to give crypt some leverage and path to adoption but it will not completely eliminate Bitcoin, that's not happening in their eyes. Crypto might looks too good but there is limitations to what each of them can do, Bitcoin can't do sustain the economy alone, it wouldn't be stable.
Instead of trying to have Bitcoin or crypto completely eliminate bank activities. Why not instead make the both to work together. If we want crypto adoption and the aim is to push Banks out of the way, there is going to be a serious challenges because the banks wouldn't allow it. Even the central banks wouldn't allow such to happen as it's designed to lead other commercial banks, they have to exist for central bank to have a successful execution and not goes to extinction.