This discussion has lead to a really interesting point, actually! The replicability of Bitcoin has always been a high concern and also point of critique for many people who aren't convinced of Bitcoin's usefulness. I also believe that Bitcoin and Gold are quite similar what this is concerned, as both their scarcities could be attacked and circumvented at some point!
i agree that gold and bitcoin are quite similar, but with bitcoin you exactly know the amount that ever will be mined. not the case with gold. also important is that bitcoin has way more room for growth compared to gold.
The supply of gold is indeed uncertain but there are ways to more or less estimate the remaining earth's gold capacity, even tho is far from the mathematical exactitude guaranteed by bitcoin, but gold is still king of wealth perception.
In addition, the scarcity of gold might be limited by time. Asteroid mining is now too expense be profitable. However when the technology is improving it might start somewhere in the future.