I have actually seen similar topics a number of times on this forum before now. As much as Bitcoin fanatics look forward to a time when banks will actually be rendered obsolete. What I can tell you with a degree of certainty is that this is not going to happen. No matter how cryptocurrencies actually get accepted, fiat will still have it's role to play in everyday exchange of goods and services. Cryptocurrency also would not be able to push out fiat and the banking system because a large percentage of the world still won't have access to the devices needed to transfer and receive cryptocurrencies.