No, Banks are already and will end up using blockchain technology. But everything is going to be in the backend. They have millions and millions to spend on development, they can just hire the best blockchain developers in the world and start integrating it on their system.
I think with the Blockchain up for some years now they are already developing their own system using it. Development is always a choice and with they have a lot of ways to improve. Digital currencies is the future and for sure, they have their own ways to develop themselves in that time.
Make sense, maybe Blockchain can't replace banks. But banks can implement blockchain technology.