Banks can't work with bitcoin, search "fractional reserve". Banks may offer some Bitcoin services in future but it won't replace fiat services nor it will be possible to seamlessly juggle/ exchange between bitcoin and fiat.
it will replace and it is possible but it takes a matter of time to happen, some points i see that it will happen is that if small merchants, businesses and department stores will integrate cryptopayments used as microtransation then thats the time will be seeing real adoption, but for now only few merchants are doing it and most happens in digital goods and services online..