Bitcoin will not replace dollar, but in my opinion bticoin will replace gold as soon as posible
I don't think also because the dollar was used as a currency in other countries especially in abroad. Maybe it will replace in a few years but it would be possible. Yes, maybe it would replace gold soon because Bitcoin also is like similar to gold. If this would happen, gold was neglected and bitcoin will be identified in other countries. All opinions are possible if the government approve this kind of situation.
I want to address that dollar is used only to places where dollar is their local currency. Foreign countries rarely accept dollars. Want proof? (This only applies if your local currency isn't dollars) Go outside and try paying with dollars. The cashier will probably just laugh at you and pressure you into looking for a place to exchange your money first. You will be forced to pay with local currency.
I also want to address that bitcoin can never replace gold. Gold is valuable because of its physical properties and bitcoin doesn't have any of those. Bitcoin isn't metallic. Bitcoin isn't shiny. Bitcoin isn't used as a hardware part of electronics.
It should also be taken into consideration that bitcoin is valuable than both dollar and gold and also has many benefits for example security that currencies like dollar and gold cannot have.