I think fiat currencies are loosing value all the time regardless of bitcoin... the price of bitcoin doesn't have to change for it to increase in value against fiat
Well probably it has a point. But then, the value of the currency depemds of what currency it is. As we can see the USD has a stable economy but then there are analyst who says that dollar is going down. But then we can conclude that today bitcoin do not have an effect.
Still, it might not be enough for fiat to continue losing its value. Currencies go down and up all the time, it doesn't mean that it will lose its value just like that just because of bitcoin. Especially not USD. It's way too big a currency to lose its value over a virtual currency just like that. Plus, there are still more people using their native currencies. Even us, bitcoin users, we still use it today because it's what allow us to pay for goods and services. Doesn't mean though that bitcoin have lesser value over fiat.