That won't happen until 1BTC equals 1kg or at least one pound of Gold. One Oz is not that much money after all (2500$ is a month's wage in the Western Hemisphere).
1 bitcoin = 1 kg worth of gold will never to be real, It means the bitcoin must be worthed over ten thousand dollars.
OP, Bitcoin is not flipping the gold. My thought if the bitcoin is different with the gold itself. The value of the gold depends on the how many weight of the gold itself. And bitcoin is not.
Gold is a precious metals and not just for people want buy for holding or invest. Can make jewelry and Is a jewel of luxury, unlike Bitcoin, just is considered as a mere value.