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.
In a way, I can understand where you're coming from. Gold has been around for thousands of years and people have grown with it so in comparison to gold, BTC is no where near perfect and I cannot see it being as widely accepted and adopted.
Another issue worth considering is that gold at least is stable and doesn't fluctuate unlike BTC. So from that respect gold remains among the standards with BTC coming no way near close. At least this is what I think, it would be great to see cryptocurrency rise to this level but this will take years!