I doubt gold holders are worried about space mining. The costs are just too prohibitive as long as we still rely on rockets to get into outer space. I don't care how good rocket technology gets. Anti-gravity would be a game changer obviously but that's still in the realm of science fiction only and I doubt will happen in my lifetime (sadly).
You're looking at this from the wrong perspective, IMHO. What I had in mind was a long-term push for the colonization and exploitation of the solar system. While I did not think of anything as fancy as anti-gravitation, I certainly did not have sending rockets to the asteroid and mining it using anything even remotely like today's technology. I was thinking completely autonomous mining complexes that would bring with them everything they need. The purpose of the mining would be to produce raw materials needed in the colonization and exploitation the outer parts of the solar system. Whatever gold were obtained as a side stream, could be dropped to the Earth's orbit along with anything else.
The context here was evaluating the longevity of gold's multi-millenial run as the primary store of wealth.