The limited supply of gold made it an interesting asset over history. Just the technology is advancing and many keep forgetting that.
We are getting closer and closer to the point such resources will be mined from other places (outer space) or various methods for easier mining/retrieving the gold from Earth can be also invented, making gold scarcity not a reliable property.

Instead something unnatural, something ensured by math to be in limited supply will remain in limited supply.
When Bitcoin history will become as long as gold's, I guess that gold will be no longer (by far) a reserve asset. And Bitcoin price? Well, sky is the limit.