Surpass is different from replace. Bitcoin can not replace good in my opinion but I do not know if it will surpass gold. Some people believe in gold because if its physical value.
All I know is that bitcoin will also be a store of value. If bitcoin marketcap later surpass gold marketcap after many years or decades, it will not be a surprise. But it is hard to know if that will become true or not.
It's really surprising actually... we see Bitcoin is currently difficult to be accepted by the majority of world governments, while gold, everyone agrees that gold can be trusted...
When Bitcoin gets the chance to be trusted by many people or even all countries legalize it like gold... we will all be surprised and see that the price changes will be very significant and it will really make the investment world excited... bitcoin will level up to become a better store of value asset than gold, if it succeeds in surpassing gold...
Bitcoin is trusted, but volitile and has huge potential to surpass gold in term of marketcap and trading volumes in near future. Gold has been here for many years, a physical commodity that can be traded both online and and physically, however Bitcoin is barely sixteen years but has achieved a greater success than gold in my opinion.
Now, the popularity of Bitcoin, and the potential of blockchain technology and its capacity to dominate faits has made many countries to be skeptic. As a matter facts, Bitcoin has given financial freedom to everyone that government faits has not allowed, hence there are fear that Bitcoin will become superior to faits.