Gold that has existed for a long time has a market cap of about $22.709 trillion. So Bitcoin has not performed poorly considering that it has been around for less than two decades. The next fifteen years will be about three halvings, $20 trillion in market cap is not a bad prediction considering the attention Bitcoin is getting. Silver with a market cap of $2.146 trillion, is already behind Bitcoin, getting close to gold is possible.
Bitcoin needs to increase its capitalization 10x to compete with gold, but gold only needs to double its current capitalization for the gap between them to become huge.
If bitcoin can increase 10x in the next 15 years, it is not unreasonable for gold to double or even triple. Therefore, there is no doubt that bitcoin can become the second largest asset in the world. But competing with gold won't be as simple as we imagine because gold won't stand still and wait for bitcoin to overtake it.