What if Bitcoin was simply the worldwide global currency? The thing you could use anywhere you travel right alongside that given country's existing fiat?
A bad comparison: You can use that country's cash if you want, or you can use Visa anywhere in the world.
Wouldn't that be a more realistic future for Bitcoin?
Bitcoin doesn't have to replace the fiat currencies but it will because fiat currencies aren't stable to support themselves. As the Feds continue to print USD like there is no tomorrow their fiat currency has become very unstable, other countries have done the same thing and the writing is already on the wall. When the world market collapses (it could be as soon as April 2014) what other currency are they going to use? Likely they will want to use something that everyone uses around the world. It could be bitcoin or it could be some other crypto like currency they invent (so they can control it).
In the end there will be Gold, Silver, Bitcoin, and possibly another crypto currency that is regulated.