I think that governments will create their blockchain and so each currency will be transformed in digital currency. So instead of Usd we will have Usd coin for Us dollar... or something like that. Blockchain grants right now a higher level of safeness. But in the future with quantm computer ( 30-40 years) things will change a little bit, but probably also any actual crypto algo will change as well..

People stopped bartering long before fiat was even invented. Fiat is just scriptural money, people used precious metal for thousands of years.

  Precisely, I think the two are compatible to work on its own individual way. Looking forward the fundamentals of cryptocurrency will difinitely give particular formation to develope its growth accommodatingly and fiat gives conveniency in a quick payments. So, I believe the two aspect will generate our necessities in separate ways.

To be frank, fiat will not be necessary in future, but the governments would keep it alive, as they want to keep the financial matters in their control and fiat is the best medium to do it.

In some point we dont need fiat. but again there are countries that really only on fiat. Its ok for most developed countries to have converted to not using fiat at all but still large amount of countries will be relaying on fiat for every day usage. We have good starting point on this but we may not see this in our life to see it. Mostly I mean to see someday payment in crypto for slice of pizza or a burger.

Everything will change and we are also included in these changes. While our technology is improving and getting more developed, our world will adapt to these technologies and use them to make their countries move with the future. I don't know what will happen  but all I know is that fiat currencies will still be there but the thing is that the technology will be so advance in the future that the fiat we usually know will be the same as the technology as the movie "In Time" but not that we will die if we don't have life but with the same currency and transactions. Just imagine how fascinating is that but still, it is necessary for a country to have a fiat. There will just be a development to it according to the technologies being made.

Market may turn digital currency and use crypto currencies for large extent but fiat currency cash will be demand and necessity will be there in future both the developments are equally important in the economy

Well, fiat will still be needed, moreover at this time the value of each fiat in a country is different. as long as the world still has scattered countries, I think fiat will always be there and needed. this is also to distinguish a country from other countries.

Fiat currency cannot easily be abolished in our economy. Although, the rapid advancement of technology can't be denied we still need a fiat in order to balance our economy. I think integration of cryptocurrency in economy will not change the fiat currency. They can use crypto in other aspects in terms of payment through online market, investment, savings etc. How about small businesses? You can pay them via bitcoin but they cannot change you through btc also. Small or large businesses are needed in our economy.