Will it be possible for Bitcoin to be like other national currency?

Correct. El Salvador has decided to make BTC be a legal tender there. So, surely BTC has become a national currency, the same as other national currencies. Even, it is already used as a payment tool internationally. However, there are still many issues related to the use of Bitcoin as a currency. In some countries, it cannot be allowed as a currency because it doesn't fulfill some criteria expected by the government.