Never. Bitcoin cannot replace Gold. We have to admit it. It may compete with Gold as a store of value and perhaps even become the preferred option for a short time but it will never replace Gold. Gold will always be gold. The preciousness of Gold is as old as civilization itself. And Bitcoin is not the one to make it worthless.
Yeah, I've always had the impression that bitcoin compares itself to gold because it's fungible and because it's teh highest value crypto. Other than that I don't think anyone actually believes it will replace gold as THE standard currency.
It's a shame countries decided to move out of the gold standard for their currencies, it's what really got us into needing bitcoin in the first place.