No it cannot replace banks, but it can be a great addition to banking system. Just because blockchain technology has its own unique things. It is much more faster, than an ordinary bank transaction. It is much more secure and banks can use it to save your funds.
I think blockchain technology can be developed and used to combine bank technology and blockchain technology, although it does not completely replace the role of the existing system at the bank, but implementing blockchain technology can provide higher security than before and all transactions will be easy to trace.