Over the long term, it is impossible to peg Bitcoin to gold. In 2140 when there are no more bitcoins to mine people will still be digging up gold from the ground. There would be a net imbalance that can only be maintained by shorting bitcoins or buying up all the excess gold being mined. Since bitcoins cannot be shorted indefinitely somebody would have to keep spending fiat to buy up gold to keep it scarce. Why would they do that?
I don't think this is what the OP was referring to. The OP was suggesting that 1
BTC = "x" ounces of gold. As more gold is mined then 1
BTC would be worth less of the total percentage of gold in "circulation" however this will somewhat be offset by the commercial uses of gold