I also believe that it can replace in the future because the cryptocurrency today is in the mainstream and even countries are banning bitcoins because they are scared that more people will turn their focus on the cryptocurrency more than working on the corporate world.
One of the reason why Bitcoin won't replace the dollar is because moderate and conservative investors are hesitant to jump into this new fad. If you manage a multi-million dollar portfolio you're going to want some proof that Bitcoin isn't going to be a passing fad. The dollar has been a stable currency for decades, whereas Bitcoin just came into existence.