I do not think that anything is replacing anything or will replace anything. For example: bitcoin is not replacing oil, gas, gold, fiat or any other thing. Bitcoin can be used as an alternative/another method, nothing else.
I agree that all such hypothetical reflections usually do not take into account the fact that, for example, gold and oil are goods that have a physical embodiment in reality and have a very real use other than as objects of speculation. Therefore, it is worth talking more about the emergence of another new asset for speculation in traditional markets, rather than about a replacement that will destroy all existing assets.
Of course, I completely agree with your opinion that among the named assets, Bitcoin is a more speculative asset, but when comparing all such assets, their scarcity nature is considered most of all. At one time, even oil began to be called "black gold", although oil has a pronounced utilitarian use, and everything depends on how much oil is in demand in the industry. But with Bitcoin and gold, things are very different. In addition, today, many people consider Bitcoin a safer asset compared to other assets, but for the time being, because when everything in the whole world starts to fall, then everything falls completely.