There are two reasons. First, Bitcoin is a non-credit currency ten times stronger than gold. So unless Bitcoin is replaced. Otherwise he must surpass gold. Second, Bitcoin is close to being the ideal non-credit currency, and it is basically impossible to have another non-credit currency beyond Bitcoin. Combine these two points and Bitcoin is bound to surpass gold
Gold has become an eternal value due to its high corrosion resistance, which makes gold 1)never disappearing metal 2)metal, which doesn't need specific storage conditions (the only problem of gold storage is to prevent it from being stolen by the others). For
BTC and cryptocurrencies, the opposite is true: 1)
BTC depends on mining facilities, which require energy for data processing, without energy supply even decentralised system is vulnerable to total destruction 2)the same for storage: it requires energy just to store data, just not to let data disappear, while the risks of cryptocurrencies to be stolen remains as high, as they are for gold. So, neither
BTC nor any other digital currency has the potential to become the new gold. It doesn't mean that they are not valuable, though. Gold and digital assets are just totally different things, adopted by people for totally different tasks.