i think that usd is more popular to the people beacuse it's the currency of america and bitcoin is just a crypto currency and use by the people in the internet.However,bitcoin is more valuable than usd 
when it come to the digital age you cannot say like that,if you look back when there was post office and fax for communication and now they are history because internet made it possible instantly ,so you never know how we will be dealing with currency twenty years from now. That's for sure. We are now thinking in terms of development and can not predict what will happen in a few years. At the moment, Bitcoin does not replace the dollar. Traditional popular currency cryptocurrency. But things can change. We do not guess.