I will not say replacement, but a way to improve their technologies yes. Moreover, this is why different banks are already working on the subject and that some have already been talked about on the proposal of the blockchain solution with banks
This is main point I also feel blockchain cannot replace banks but this could be revolutionary for them as many changes will happen in banking mean transactions speed could be fast fees could be low but banks still going to do work as they are on blockchain is just a system which will increase good things for them.