This is very possible. The Blockchain technology is a revolutionary one with a lot of significance. As the people become more familiar with it, the adoption and utilization of the Blockchain and cryptocurrency will increase which will gradually lead the world to cashless.
I am sure that the blockchain is able to change the world. But I have doubts that the development of the blockchain will lead to the disappearance of fiat money. Most likely, cryptocurrencies and fiat money will exist together in parallel. There are many countries in which there are problems with the Internet.