I believe that is going to happen for the next generations. Because it all started with paypal, people can buy things all over the net without using cash.
And since we are already in the technology days, I do believe that there is going to be a cashless society in the future.
But I don't know when it is going to happen that paper money is going to become totally lose.
I agree paypal is still depending on fiat because you aren't going to have balance to your paypal if you are not going to use fiat money.
I guess the same thing in bitcoin that is going to be a total digital currency and does also need to have fiat if you are going to buy bitcoins.
But in the long run that is going to make paper money because of these innovations.