Imagine that one day someone finds a chemical way to turn matter into gold. Everything would lose value instantly.
That's like saying "Imagine that one day someone finds a way to make Bitcoin insecure?" This is highly speculative. No reason to believe that it's even possible.
Actually, transmuting material to gold is already possible. You need to remember, even the gold we have today was not originally gold.
It is not very economical at the moment but billions are being spent on cold fusion research that has the potential to poop gold bricks out as a waste material.