Bitcoin will never defeat the dollar. All due to the fact that the dollar (or other national currency) is supported by the government. And bitcoins are supported by people. But the government has the authority to issue laws that will make bitcoin unprofitable. And these laws can be adopted at any time
It is not about defeating the USD, it is about upgrading it.
Yes maybe not now but eventually they will need to. Without the trust of people in their currency it will not work.
If only people would know how they are doing it and making them realize that it is just the government who is really making a profit out of fiat then they will be against it.
But just like I said before. It became traditional that they cant let go of it.