Although by "paper" you probably refer to "what the paper represents" and not the actual paper itself...recall the United States destroys tons of paper bills every year because it physically gets worn out. In fact, didn't Canada experiment with a new, thin, plastic dollar? I remember seeing that on TV one night.
No matter what medium backs up the currency of a nation, it will always symbolize the "atom" of that nation's "unit of work," and therefore will probably always be with us.
We need some paper money yet, but in the future, our technology and innovation can invent a virtual money. Just like you are saying, for this day, our money is paper, and what if in the future, our money becomes virtual money, or cannot be seen through our own eyes. I think it can be invented after a few years, we all just need to be on the right track of using it.
It's always nice to have something "in hand." A system that is entirely based on virtual transactions runs the risk of total collapse in the event a loss of centralized data, or if there's chaos once the system is restored and people disagree with the new accounting.
Still, it's hard to argue against bitcoin. It has made tremendous progress due to its wide range acceptance.