Gold is certainly an investment that will continue to grow and value, this is because Gold is always the first choice in investment, gold is never forgotten and is always discussed by people, more than 7 billion people in the world can receive gold and I'm sure the price of gold will continue to grow.
Gold might have real world use cases as an useful material, but argument of gold being first choice because of that and scarcity doesn't hold water after we start mining from asteroids. And this is not science fiction anymore:
Nasa's Psyche missionWhen you flood the markets with gold, it would drop the value so much it would absolutely crush the gold investors.
I am not saying that we could depend just on scarcity either to back up value but it helps, there are many factors that need to be available like stability of working infrastructure to keep values stable.
It is definitely not science fiction at all. It is something that is "possible" but it won't be that easy to do. We may not really benefit from it because by the time they actually start mining them and bringing the gold back to earth, we will already be quite old. It is something that our children and their children will benefit from for sure. However, one thing that we are still having trouble with is food and water.
The whole world is paying a good chunk of their income to food and maybe that’s not a problem in big nations, but as you can see from Latin America, some parts of Asia, a whole big part of Africa, the basic human needs are not met in some places, so you can have as much gold as you want, but we first need food and clean water all around the world.