It would take many years to achieve this and maybe it will even never happen.
I agree with your second option that it might won't never happen, because people believe in USD, and the bonding is more strong. BTC is very good, but replacing USD seems quite tough and nearly impossible.
bitcoin will only be an option for the world community that's what I see
I also agree with the fact that Bitcoin will never be approved by the government. And the more the government will never allow Bitcoin to replace the dollar. Bitcoin will benefit people on par with the dollar, but the government does not take
But it will need a lot of the research about that. and it seems like still long to go.