I do not think bitcoin can destroy the banks. People do not change their habits easily. They also trust the bank too much. If the bitcoin starts to be used by a few billion people around the world, the banking system could end up.
But the states will not allow it. States always support systems they can control.
I think that's far from happening. Just imagine how many bitcoins are there, and if billions will be sharing it, then everyone will be getting a few thousands satoshi. It's not that the state wants something that they control, but it's all about the ease, and what's good for their economy. Bitcoin could help the economy, but as a currency of a certain country, it's hard to happen, but in banking, it is possible.
