Ofcourse not fiat will be here in the world except bitcoin just release its own hard money i mean real money in the real life not just in internet bitcoin can do so but if the bitcoin stays in the internet theres no way that bitcoin can replace or remove fiat money in this world.
We see today that besides Bitcoin they are starting to create other crypto-currencies. Some countries also go the same way to create something of their own from decentralized currencies. But nevertheless, the Fiat continue to live and will only be the only natural currency for daily use.