For all we know, technology is rapidly innovating over the years, and we will see a lot of improvement, discoveries, invention anytime soon.
So, for the question, if blockchain can replace banks, it's a big 'No' when in fact some banks are seeing the potential, advantage, transparency of blockchain, so they are checking, reviewing and studying it how they can use it in bank transactions.
Maybe we should consider asking a question something like "what can bring blockchain that will replace banks?". if we associate answer with decentralized system and possibility to get rid of the intermediary agent - it's not so simple because banks are businesses and their owners definitely don't want to reduce their income and money, so it will be really hard to replace banks despite presence better technologies.
Replace bank by blockchain is not easy because many participant bank never hear with blockchain technology and adopt for bitcoin and altcoin transaction, how ever for participant have older year very hard how to use bank if adopt with blockchain bitcoin and altcoin, how to sent and how to receive money if using bitcoin and altcoin, now keep bank at the same place and give space for blockchain become legal currency payment.