Diamond prices are down 60% since a 2011 high, and they are still falling. It's not all down to lab-grown diamonds, demand is down too, especially in China.
No one can lab-grow gold yet, so its rarity and scarcity protect its value, but that will end too. It's just a question of when. China launched an asteroid touch-down mission this week, which will make it the 4th country/region to do so, after Europe, the US & Japan.
How soon will it be feasible to mine asteroids? Who knows, but a breakthrough in space propulsion might mean the prospect happens quickly when it does. It's possible gold has twenty years or less of being high value left.
The $80 Billion Diamond Market Crash Leaves De Beers Reeling
Gold has plenty of uses, besides being shiny and easy to work with. Imagine if all your electronics used gold traces because they were so cheap. Imagine if the windows of your car were coated in gold like on an airplane so you could easily defrost them in the winter rather than blowing air at it in the front and potentially distracting lines in the back. Imagine if gold was the filling of choice since it has a similar expansion rate to teeth. Gold has a number of applications in space. Ever wonder why the JWST is that color?
There are plenty of things gold would be excellent for if it wasn't so expensive.
https://www.statista.com/statistics/299609/gold-demand-by-industry-sector-share/
Only 7.16% of gold usage is for technology. The other 92.84% are just for purposes of being shiny. If we dropped gold from jewellery and as a proxy for money, there would be more than enough gold to go around and the price of gold would drop a lot.
Why are you surprised that the really expensive item isn't used for utility purposes? Why do you think its use wouldn't change if it was cheap?
Before aluminum was cheap to refine, it was used for cutlery and other displays of opulence. After it became cheaper, we used it everywhere.
Still not enough to use gold instead of copper for wiring
I don't think gold would make really good wiring.