Over what time frame? I can see them coexisting for a while. Power structures can impose currencies. But I think it will soon be very difficult to create a new national currency when the old one fails, because a Bitcoin economy can spring up naturally very quickly. It will also be hard to maintain a national currency with Bitcoin waiting to precipitate a bank run if the national currency is abused.

Preventing Bitcoin will require strong authoritarianism, which is not an efficient means of governing and will lose out to more free economies.