I never think that Bitcoin will be able to replace the US Dollar because I just do not see something like that happening. The US knows what they are doing.
Bitcoin does not need to take over the US Dollar, it needs to walk on its own path.
Exactly, bitcoin really does not require to replace any other currency in the world but it should make its own identity among the countries which are currently using other currencies like USD or EUROS for trades, if bitcoin can do that, then it can really become the strongest currency of the world.