Boycotting merchants who don't use BTC as their unit-of-account will prevent mass adoption. Thus we can now be sure that BTC is converting itself to fiat. And anyone supporting BTC and claiming it helps us get away from fiat is just full of BS.
It will depend on the quality of fiat. For the majority of the countries out there BTC is better than hard currency like the USD or EUR, because in many cases they have restrictions regarding foreign exchange. Convertibility to better quality fiat, which is regarded as "stable", is another issue though. But EU and USA are like 1/10th of the world's population, not 100%.