i think that nothing is impossible. The problem is only time, and time here will be counted as a millennium or more and I do not think we'll be alive to see that happen. But now I can be for sure that in the near future, bitcoin will replace the dollar because eventually everyone will use bitcoin.
You are right in bitcoin anything can happen any time because the use of the bitcoin is increasing more and more. The people who were not even accepting bitcoin are now ready to invest money in bitcoin. They are making good profit using bitcoin they will make the bitcoin more popular if they will start promoting bitcoin on TV as well I hope soon bitcoin will become the legal currency.