Even the Central banks are buying more Gold (+13% from the previous year). Economists predict a dark year for 2019 and it seems a lot of large funds are now buying Gold massively. Especially from Asia and Soviets.
There is not enough gold in the world to back up all of the money. People can still value it, but I doubt they can use it like the US did. What could be done instead is using cryptocurrencies after dollar collapses, because they are naturally limited and don't need any kind of backing up. Well, a weird but not impossible thing would be to back up fiat by cryptocurrencies. I guess this would be the situation gold and dollar used to be in. It's not such a bad idea in case people come to value cryptocurrencies themselves. Fiat was a bad idea, and something has to replace it. The crash is probably inevitable...