If everyone in the world gets into crypto and cryptocurrency will become an official global currency, do you think bitcoin then will stop depending on fiat currency? Or will it just co-exist with fiat?
Bitcoin doesn't depend on fiat currency, period. It can be exchanged to fiat and could be used for similar purposes overall, but they are nowhere near interdependent, at least in theory. Bitcoin as a cryptoCURRENCY and fiat are competitors in the financial market for the spot of exchange value measurement tool.