I don't think so that it is possible in next few years or so.
There are still many issues to be sorted out before its world wild acceptability. Some concerns are:
Crypto currencies are highly unpredictable/ volatile.
A crypto market is not regulated by some regularity authority so there is no one to safeguard the interest of small investors.
As some large selling and buying is observed or some news is broke, crypto market reacts very fast.
Decentralized technology is still new to the world. Its market penetration and adoption is still negligible.
So in future a more countries will jump into it and it will gain more trust of people. Its value will also increase but not sure that it will be so popular to replace the fiat currency in near future.
