Digital currency is basically a threat to the old conventional paper money, as the world is heading toward the cashless society then paper money will surely feels its effect.
Indeed, the bitcoin has a good future because its digital with the paper money this is most likely the opposite it has a bad future because everything is gonna be digital.
I think the paper money will soon or later disappear.
I doubt that paper money will disappear anytime soon, there are too many people that would be in opposition of taking paper money out of the economy. There is a good feeling when you have cash in your hand as well, so I wouldn't want to see paper money phased out either.