wait for parity, than exchange some bitcoins for gold
But what do you mean by parity? If you mean the price of BTC in dollars is equivalent to the price of an oz of gold in dollars, that's rather meaningless. Or, do you mean when the value of all gold in the world is equivalent to the value of all bitcoins? Now, that is meaningful, but also not likely to happen very soon...but, you could pick a target ratio of the value of all bitcoins in existence to all gold in existence. That would measure the usage of bitcoin relative the usage of gold.
