Honestly, we need to be realistic so we will know the real answer. Bitcoin in any way cannot replace Dollar because that currency is too powerful and I even doubt if we can replace a weak currency. The thing is, we do not belong to their level since we are decentralized while every countries currency has their own government to protect and to improve theirs.
At the current moment bitcoin is a weak currency, but things change dramatically in this world. You never know what happens any second. People are getting famous just by posting a single picture or video these days on social media.
So, we should not deny the fact that It may possible in future like 10 years from now. Bitcoins may make an impact in the market and people believe and start working on converting dollars to this currency.
I agree with Natalim, and a little bit for rickadone, it seems like bitcoin will not replace dollar 95% vs 5% that bitcoin could become a major currency and used by everyone in the world, more than dollar could achieve in the future maybe around a century.
Bitcoin cannot pass a country regulations and a government could ban bitcoin as some countries have implemented the restriction.