There are already companies that keep bitcoin as reserves; in time, banks will also have to adopt this since they can't beat the system and will have to join it.
Check out the list of companies using Bitcoin as reserves; it might be outdated somehow, as I believe companies like Tasla might have sold out some of their Bitcoin reserves.
This could be the situation in the future as many companies already started to work with this,
We know that fiat currency are being controlled by the government and being manipulated, if you hold too much of this the government will always have the control over you. Theres a huge chance for Bitcoin to be one of the global reserve, though my only concern here is that those companies will become whales and that could also affect the cryptomarket, especially when it comes to price manipulation.