I do agree that bitcoin cannot replace the fiat currency. The government will not allow any currency that they cannot control to replace their own national currency except if there is economic collapse. But if you notice countries are now making their own cryptocurrency such as Sweden, they are the first country that have launched the first ever government owned cryptocurrency. Soon other countries will follow their footsteps and eventually will be used by people. But even though bitcoin will not replace traditional money but it will be still used worldwide.
Bitcoin will never replace our traditional money. Yet, it has a big potential to become our world currency that may used in all market and industry. Furthermore, we all know that fiat is our first currency and I think some government will not allow to replace it. I think in the near future some government will allow cryptocurrenct to become one of their currency.