As DAT pointed out, the balance of payments will push capital flows toward essentially the same distribution as exists now. There is an excellent, albeit lengthy explanation by FOFOA entitled It's the Flow, Stupid, and it's follow-up Flow Addendum.
What it boils down to is that gold can act as a store of value and a medium of exchange or a metric of value - but not all three in perpetuity. Fiat can function as a medium of exchange and a metric of value, but not a lasting store of value. No form of money has ever been able to act as all three at once. The limiting factor for gold is its physical manifestation. This is explained best by the Triffin dilemma.
Bitcoin, by being entirely abstract yet functioning almost exactly as gold does, is capable of satisfying that issue entirely because it is infinitely divisible (in theory) - in other words, Bitcoin can act in all three capacities simultaneously. The Triffin dilemma would be solved, and a unified currency finally possible.
Going further than this, even if gold were to continue as a reliable store of value, there is the possibility of massive price shocks looms within our foreseeable future. Bitcoin's hard limit of 21mm units virtually eliminates that kind of structural supply shock.
+1. Not to mention Fort Knox hasnt been fully Audited since the 50's, who knows how much gold the US actually has, or that everyone else reports it correctly. Rumours abound that 250tons passed through Hong Kong to mainland China in 2011 and has not been declared by their central bank....Gold reserves are nothing to go by.