There's no chance btc can become a national currency. Why? It's because first of all, there are the banks who would protest and of course the government will definitely won't allow it. The threat of money laundering is always present with btc and that will always be the case that the govt will reason out. And besides they have no power over btc. They cannot control it and iy can also be used by politicians who don't wish to share their net worth most especially if they are involved in illegal transactions.