For me, as of now it serves as an international currency. Why I said so? It is becayse bitcoin is widely used on a lot of cluntry in the world. Tgey either use it as an alternative for money in the internet, or as a form of investment. Which I might say is wise.
Being a national currency is not for bitcoin right now. The priority is gettind adopted by the entire young community. Then we can discuss this things later on. This is my personal belief.