Could it be possible that in the future there are countries that use bitcoin as the national currency??
no. Bitcoin is decentralized, and the government will avoid anything without a full control. It is too risky for a country if the national currency is something decentralized like Bitcoin without full control over the governments. Even though there is a good side, I believe there will be a lot more of bad side.Japan is already doing this 
. Zimbabwe is another country that could do this and so is Ireland. As of now it's really difficult for any major country to come out and make it, reason is most of the country's are keen on banning it. So there's little change to see this happen anytime soon, few years down the line I feel yes.
I don't think the government fully accept Bitcoin as a payment system for their country. It just the government is in favor of Bitcoin.. Zimbabwe is another country that could do this and so is Ireland. As of now it's really difficult for any major country to come out and make it, reason is most of the country's are keen on banning it. So there's little change to see this happen anytime soon, few years down the line I feel yes.