BTC was created with a new transaction system without a central authority. The BTC can be used in the future as the main currency that we gonna pay with. But what's gonna be the value of a main currency? What's the value of dollars or eur?
-Answer is: The dollar IS the value. The dollar doesn't cost anything. The dollar is the value.
If BTC is gonna be used in future, it not gonna cost anything, because the BTC is gonna be the value. It not gonna be like Bitcoin cost 50,000dollars... Bitcoin not gonna cost anything because Bitcoin IS the value. But that's probably not gonna happen. We not gonna pay with BTC but with stable coins like USDT...
I don’t think Bitcoin being the “main” currency could happen and it’s impossible in my opinion because of the price’s volatility and unpredictability. Fiat is still going to be the main currency and it will not go anywhere because the banks would remain for a very long time. Both fiat and crypto can coexist because they have different use cases.