What are the chances of living in a world with no actual money ? 
Low. I think personally that cryptocurrencies wont make FIAT useless, but I think that cryptocurrencies will work hand-in-hand with FIAT money. Especially in countries like the United States, and the other first-world countries; I don't see FIAT going anywhere soon.
Yup, I agree with mjglqw. The usage of cryptocurrencies is beneficial to those who has access and knowledge about it, otherwise it's worthless to those who does not have. We have been using fiat for the longest time I can remember, and for it to be completely gone would affect the society drastically. As mjglqw said, fiat and cryptocurrency can co-exist and help one another for the betterment of the economy. Mass adaption won't also be a complication to experience since fiat will still be existing alongside crypptocurrency.