So as far as we know BTC currency is growing wide, do you think there will be when it become a national currency?If yes, why?If not, why?
I think it might be possible because bitcoin comes with so many benefits and advantages that might be any country's whee it's people will use more bitcoin than regular Fiat will make it their national currency. I believe that you can not predict anything in case of bitcoins. But with due time there are very chances that people will invest more and more in bitcoin. So there are possibilities that it may become the worldwide currency. The system of currency is running from so long. And this digital advancement is the knock of future on our door steps.
National currency means this currency can manage by the government or the national banking system. You forget the government can not manage the transaction of Bitcoin if the business want to evade tax. Because the business do not report the total revenue from their business, the government will can not tax them

This is pretty hard for any government to make bitcoin their national currency and the reason is very obvious. Governments always want to have good control over the assets of the country and wealth or people. If bitcoin is their national currency, they wont be able to charge have taxes and in that way people will know more be answerable to them for using any services or purchasing goods.