I think you are a little too enthusiastic with this. If you think it trough, when everyone has more money than he can spend, hyperinflation is the logical follow-up, as people will want much more money to do hard work.

And it's not the banks that will fight back, at some point states will have to protect their currencies. And rich as blockchains can get, states hold the real power, based on people and armed security forces.

I don't think it will come that far though. The blockchain is a wonderful technology that enables decentralization. But it's arrogant to believe that decentralization is beneficial for every single thinkable application. I think cryptocurrencies and fiat will at some point coexist as equals, each with their preferred field of application, but none will extinct the other. To stay at your examples: music, films, books are still produced by centralized corporations, even though they are copied/distributed after publication.