bitcoin cannot replace currency in the world because price is not stable.

currency should be more stable.

you may reply me. currency is not stable also but you should think  

USD currency price is up and down 1-2% in 1 month.

bitcoin price is up and down 20% in 1 month.

what will people think if they just change USD to bitcoin then their money down 10% in 10 minutes?

bitcoin can become stock but cannot become currency