bitcoin will never replace the dollar. Why? the government will never allow it to. If governments feel threatened by bitcoin, they will push it into a blackmarket currency, to protect their own currencies.
That's perfectly said, bitcoin has no power as it is only dictated by us and we are bound to follow the rules of the government and they might impose anything against bitcoin. Let's be thankful of what we see now, bitcoin was a successful but it's a different currency and will never take over this world.