You ask as if this isn't already happening. See Facebook, Signal, some banks, power and electricty companies (telcoin, electroneum) Also many of the blockchain/crypto projects are themselves companies of various sizes, building real-world business involved with the crypto they're producing.
What happens is that people use tokens with varying degrees of de/centralization, and occasionally prefer them over the currencies of their own countries.
What happens to these people, and speculators, varies, and depends on the level of centralization, whether the central control is used in a manipulative way, and finally whether the crypto in question has economics grounded in real-world use cases which will drive demand independent of speculation.
What happens is that people use tokens with varying degrees of de/centralization, and occasionally prefer them over the currencies of their own countries.
What happens to these people, and speculators, varies, and depends on the level of centralization, whether the central control is used in a manipulative way, and finally whether the crypto in question has economics grounded in real-world use cases which will drive demand independent of speculation.