I think it is possible that people will be using digital currency as a payment to buy goods, paybills and many more in the future. But i think not all countries will go cashless lile china because they hate QR codes and crypto, so it will take a lomg time before everybody will be using digital currency.
Some countries have their own rules for valuing virtual currencies at this time but we will see in the future that all will have a type of virtual currency that you can use anywhere and anytime.
Yes, every country has different rules in accepting cryptocurrency and there are still many countries that have not legalized it. Every country has virtual money is very possible but it takes a long time for this to happen. Even though that happens, real money will never be eroded by virtual money.