I am a fan of Bitcoin, but I am realistic, Bitcoin is not yet suitable to be an alternative global currency due to known problems in the network such as scalability, speed, and high fees.
Bitcoin carries in its structure the specifications of the main global currency, not the alternative, but there are problems that must be overcome first. Imagine, for example, if global adoption occurs and there are millions of transactions that occur every second on the network, what will happen?
Of course, Bitcoin in its current state will not be able to process this huge amount of transactions at the required speed, in addition to price fluctuations that make things more difficult.