I think one of the big obstacles to totally replacing fiat money is that people are used to the pricing of fiat.
Back in the 80s, there was a campaign to try to get Americans to dump mph and go with kmph , etc
pounds for kg...and it never caught on.
Would people dump fiat pricing for btc pricing?
There so many retired people on the earth not everyone can get used to bitcoin. Only next generation could be using bitcoin as "main" currency and at our situation FIAT money wont go anywhere. This will take time.