Bitcoin can only be a global currency only if every country recognize this thing but I think we need more time for that. Bitcoin is a first cryptocurrency and i believe it will continue to spread around the world until it recognized and acceptable around the world.
The government will always know about technological and economic developments. They have decision to bitcoin it's not mean they didn't know bitcoin and cryptocurrency, because before deciding to ban or accept cryptocurrency they will control feasible or not feasible if acceptable in their country.
They will always have a reason why banned bitcoin. And it is very unlikely for those who banned bitcoin now and in the future they will accept bitcoin and cryptocurrency. They will stick to the first decision to ban bitcoin, no more.