The simpler the currency for circulation is, the more reliable it is. Therefore, a global international currency is unlikely to be based on the Internet. Although nowadays most of the payment systems work using the Internet. High technology is very vulnerable to various disasters and natural disasters. In order for the financial system to work effectively in different conditions, it must have different channels for transferring the means of payment, and not only with the help of the Internet.
Of course internet-based currencies will not be able to be applied simultaneously throughout the world, because each country has problems with the internet network, especially in developing countries.
In developed countries, maybe the internet network is not a problem because the infrastructure is good, so that internet-based currencies can be applied but still as an alternative. The main currency remains fiat because it is physical and is easy to use for all people. Besides that fiat money is easily monitored by the government.