The Blockchain and the Banks operate on two different models, one is centralized whereas the other is decentralized. Each has a unique feature the other cannot provide. Replacement of the bank by blockchain seems quite impossible but the worst that can happen in the future is the banks coming to accept Blockchain technology and its cryptocurrency in its operations. Right now, what scares the banks is the decentralized nature of the blockchain which is capable of giving power back to the people in terms of financing(no authoritative third party interference).