Yeah, I don't see any threat to paper money from bitcoins, as the users of paper money are in huge proportion, comparatively very few people are using bitcoins at present.
You are definitely not seeing this from the bigger picture. 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. The world doesnt really need the old conventional paper money anymore because there are alot of cashless form of payment and someday it will be taking its toll towards paper money