so it will take a long time for bitcoin to take the place of the dollar, but at some point, bitcoin will definitely be more popular than the dollar.
Dollar will be there. You need a dollar to scale/calculate your Bitcoin value. Both could be the same in terms of popularity. But I do not think Bitcoin will take over the dollar anytime soon. Do we expect it? I don't know. But where there is a good side, the opposite exists as well. But we don't know the future. You could be right as well.
Both the currencies can all exist together but in future, one will outshines the other and we already know that currently with what we are having, everyone is after the use of a digital decentralized currency and bitcoin is their target, we have to also know that bitcoin is not fighting this over dollar, it's only existing as an alternative in which the people preferred it to the fiat traditional currency as of now, very soon it will revolutionize financial economy globally and even countries we least expect will adopt bitcoin as a legal tender.