The real argument is 'could there be an absolute cashless society?
In my opinion, it might not happen.
Our economy believes and depends in the current banking system.
But Bitcoin revolutionizes/ing a part of economy, let us go along with it.
Living in a cashless society would be a very hassle free and easy to live life. Some rich people are already doing cashless but they are only few compared to the total population of whichever country they belong especially in the third world countries. Having bitcoin as mode of payment is possible but total cashless will take a lot of effort and years to implement since not all people are fortunate to have internet access and smartphones.
True, many thing need to be done for this to be used not just be rich people but we are close to it. But think that main problem will be third world countries if this goes on global scale. But think that this will be solved cuz today technology can do this.
Without a massive campaign it will take too much time yet. Some people don't know how to access computers and internet, so to deal with Bitcoins will be much harder to learn. I believe this cashless society will work only when we reach to the status those futuristic movies show, where people have flying cars, laser weapons and strange clothes. On that time the technology must be advanced and Crypto-Currency must be accessed everywhere in the globe.