Firstly, come down to the ground because you are currently sitting on an imaginary issue which doesn't exist!
Understand the below facts,
1. crypto is not a magic wand.
2. Crypto is not created to bring economic overhaul
3. Crypto doesn't have the power to become global currency
4. Cryptos are literally a piece of code
Now, lets look at the possibilities,
1. Virtual currencies will take over the world economy which will be created and circulated by the central banks
2. Banks will have to bring in major technological changes in their operating structure to cope up with the changes
3. World will never move to "one world one currency" regime
4. Banks will still control the economy
5. The parallel economy created by cryptos, will get merged with mainstream economy after banks and governments realize that it's impossible to stop them
6. Crypto enthusiasts will keep the revolutionary ideas in heart but continue to live in reality
Constructive criticisms are welcome!
I don't understand why you only mentioned these points. Fact #3, for example, is true for now, but it's not like it is in principle impossible for cryptocurrencies to replace fiat currencies in the long run. As for #4, one could respond that money is literally a piece of fabric or paper with numbers on it. Code seems more reliable.
Now to possibilities. I don't think it will be just one of them. They can get combined in various ways. And it's not necessary that either banks will make their own "cryptos" that will dominate the world or two economies will merge because the banks won't have any choice.
For one, fiat could indeed become a thing of the past. And banks could find a way to benefit enough from actual cryptocurrencies, and thus change their policy towards them willingly.