I voted for both work in parallel as I think there should be a good and healthy mix of both.
A hybrid, so to speak, that uses the advantages of both.

Governments never want to give up their power, but humanity realises how much they are restricted by fiat currencies.
Therefore, I think there will be a Central Monitoring, but it will be very easy.
We just have to consider what advantage governments could gain from crypto currencies: 
- More trust through mathematics and cryptography.
- A consensus that is irreversible.
- and, last but not least, perhaps the greatest strength is transparency. Thus every citizen can be tracked easily and governments can see when and where someone spends something.

on the other hand, cryptocurrencies are still new territory for many people and higher politicians. Therefore it will become a slow process and both will coexist for a longer time.