Just want to point out things. Ofcourse Bitcoin can be traded to fiat currency through exchanges. But in contrast, even if something do not have an equivalent value to fiat, it still has a value. One example is trading in the early years of the economies. They are trading goods to Gold, since there's no "definite" currency system before. And since there is already, fiat will always be the basis of something if it is about its value. Actually there's another way, which is through mining, bounty campaigns, and the likes in order to earn Bitcoin and other cryptos.
Bitcoin is a version of fiat currency based on its usefulness, function and value which are being done through fiat currency. But I doubt it is the complete version of fiat. Decentralized, volatile market value, scope of area wherein it is widely being used and likes.