I want to point something extremely important that most people overlook: Bitcoin is a payment system more than anything else.
The currency aspect is just one of its features. Without the payment system, bitcoins are worthless. No matter what happens to the value of a bitcoin now, if the payment system fails to gain acceptance, a bitcoin will be worthless in the future.
Bitcoin is thriving at $115/bitcoin. I would have to argue that it already has gained acceptance at a payment method and can only go one direction.....UP.
Don't be fooled by the price. Bitcoin didn't go from $12 to $115 based on its acceptance as a payment system. Most of that rise is due to the expectation of future success. If Bitcoin doesn't succeed as well as people expect, the price of the currency will fall.
Furthermore, people can't to expect the value of the currency to rise forever. At some point, the industry built up around the Bitcoin payment system must generate enough income to keep it in business or it will fail. When people are no longer depending on the currency to rise in order to make a profit, then we can say that the payment system has gained enough acceptance.
The success of the Bitcoin payment system is ultimately what will determine the value of the currency.