I am not sure . dollar and fiat currencies still has its own strength. I think bitcoin and the dollar could together build a system in the world economy. dollar became the main media in the real world and bitcoin as the main currency in the digital world.
Dollar is only depending on the petro-dollar system and once it falls, dollar may collapse. it is just a matter of time before that happen. but bitcoin wont replace it. a new fiat currency will emerge and people will trust it again