it is not possible for fiat money to disappear. the world cannot funtion only using virtual currency. and most of the people do not trust on virtual currency. and it will also be difficult to exchange bitcoins for day to day purposes. it can be helpful in many ways but due to certain boundation virtual currency cannot be only currency used
If you're around 20, your generation will experience the replacement of paper money to digital currency, that is for sure. Right now it might be hard for people to trust virtual currency, but they accepted a lot of digital businesses in these coming years, bitcoin will be adopted too. Its alright for it to take time, we are talking major revolution here, doesn't happen in a week. And sorry but exchanging and trading bitcoins is so easy already, I think it will be so much easier in the future. Don't trip bout that.