I don't see the devaluation in the fiats as a result of more usage of the bitcoin/cryptocurrency. The only time it can affect the fiat is when and if the bitcoin is fully adopted as the main currency being spent in a country. But at the moment, we are not having this as the cryptocurrency is still finding its feet fully.
I agree.I'm sure the government will not permit this to happen.It will always make its regulations for cryptocurrency.For now,i still don't see the competition between cryptocurrency and fiat currency since there are still only few countries who have adopted bitcoin already.But once mass adoption happens,this issue will sure to be reopen.