I never said the rates wont fluctuate, obviously they will. But you mentioned how one currency "won't compete" and that's bollocks. Free exchange will keep both currencies in check, fluctuations and all. Prices will shift, and exchange rates will change, but in the end, both currencies will have relative value.
But feel free to tell the economics experts over at Blizzard they're idiots.
You said currencies don't compete with one another, therefore exchange rate shouldn't fluctuate. Please keep up.
And pure free trade always eliminates the lesser entity. Intervention with that free trade in the forms of policy and regulation is what keeps the dominant entity from killing off the lesser one, or "keep both currencies in check" as you put it. According to Jay Wilson, Blizzard will have little to no influence on the value of gold. If that holds true, then eventually gold will devalue to as much worth as it is needed to run basic gameplay mechanics such as repair and buying potions.
I actually believe economic experts at Blizzard know exactly what they are doing. In another recent interview, Jay Wilson said he expects players to eventually lean towards RMAH and trade with e-balance. That means Blizzard expects people to eventually switch from gold AH to RMAH, and they will be charging transaction fees from those who have no choice but to trade with e-balance, therefore massively increasing profit.