you shouldn't even be comparing bitcoin and gold because they have nothing in common and not in the same category for one to replace the other. bitcoin is a currency and gold is many things but not a currency. gold will remain as it is as long as it keeps its use cases which it will. and bitcoin, as a separate and entirely different thing will grow only as long as it is offering what it is suppose to, meaning a decentralized secure payment system that is censorship resistant.
With the growth of bitcoin, crypto currencies, blockchain technology and more widely acceptance of crypto currencies globally, bitcoin will have better position in global financial areas. Bitcoin is a volatile asset, yes, but as we all witnessed so far, bitcoin has gradually become a new reliable channel when wars, conflicts occur.
I agree that there is no common thing between Gold and bitcoin, and they actually have different customer populations too. The elderly will have difficulty to assess term of crypto currencies, bitcoin, wallets, and more things, so bitcoin has still been more favorite by younger-generations. The elderly, includes investors will stick with Gold, but the young investors might prefer bitcoin, instead of Gold.
Generally, both Gold and Bitcoin will do exist together in human civilization.