Bitcoin will definitely take over the gold in future, gold is more preferred only because it exist since long time and majority of people are not aware about the bitcoins yet.
i don't think anything can ever replace gold because it (very similar to bitcoin) has multiple functionality. gold is not just and investment you make money from it is used as jewelry, in many real life applications and many more.
so although i think bitcoin will get huge in the future but i doubt it can replace gold.
Its not about replacement, it all about investment, we need to pick the best which best suits us, we don't want to see bitcoin and gold replacing each other, we should take advantage from both of them.