I believe that a lot of Fiat currencies are in for trouble in 2015 - Russia, The Euro, Turkey, Argentina, Russia's satellite states (such as Belarus) and even some Asian currencies mixed up in the devaluation currency war between China and Japan.

But of all the currencies out there, I think the USD has the biggest chance of thriving. The US has the biggest economy, it has the most advanced military, it has the rule of law, it has a crap ton of food/resources and it has a strong, dynamic and growing economy.

Think about this - where would you want to keep a couple million dollars for 5 years? In China it can get confiscated, Japan is a QE freakshow with a declining population, in Russia your fate is tied to Putin and Oil, the Eurozone is about to go through some serious shit with Greece again, and most other places (except for the tiny nation of Switzerland) are a complete gamble. I don't get all these "US dollar will be worthless" people. The USD is the safe place to keep big pools of $ long term - bearing any major unexpected political or social black swan that knocks America down a peg or two.

The people who need BTC aren't Americans, its those poor bastards buying toasters and flatscreens to try to save their quickly depreciating savings.

Just my 2 cents.