I agree that the Bitcoin niche will remain small, for quite a long time.
People are very comfortable with using regular money; they see no urgent need to adapt to using Crypto-currencies.
It would be more of an inconvenience to them at this point, even though they could save a little, with low transaction fees.
Define long time? 5 years it has taken to become more powerful than the US dollar (400 times more buying power)
Perhaps you forget the United States have only been around for 238 years, and that the world is billions of years old.
Bank notes were first printed in 1661 (not long ago) in Europe "Stockholms Banco in Sweden was the first European bank to print banknotes. The bank was founded in 1657 by Johan Palmstruch and began printing banknotes in 1661."
So you need to be more clear about what "a long time" is. The blink of an eye my friend, that's how fast it will happen.