Fiat currency will always dominate because it's what we use in our daily live for purchase of goods and services in this country. Petty traders and illetrates wouldn't bother to adopt bitcoin in their businesses because they don't see any reason for that.

However, bitcoin wasn't created to take over from fiat but to be an alternative currency to fiat. It's only people who have taken care of their basic needs and still have extra that can invest in bitcoin. Paper money is easy to use in buying stuffs face to face than bitcoin.