If there is mass acceptance, dumps won't be necessary. He won't need fiat.
A lot of people don't seem to understand that if Bitcoin is successful it will be
the money - currency trading as an industry and occupation won't exist any more because there won't be other currencies to exchange.
That is just idealistic bullshit.
Bitcoin can take a major part in the world without destroying fiat completely. There can also be other cryptocurrencies besides bitcoin.
Bitcoin will definitely never be the only money on earth.