For me personally, I think its possible for the government to ban bitcoin if they can all agree to(that is the entire government of the world), but on the other hand, the probability of this ever happening is very very low, like if I should put it in percentage, i would say that the possibility of the entire government of the world banning bitcoin is 0.00001%, this is because it is practically impossible for them to, for several reasons, and one of them being that ..
Ego and pride will not allow them work together in one accord ..
And also, as some countries hate bitcoin and seek to ban it, there are other countries that like it and seek to legalize bitcoin in their country too, so this conflicting interest will never bring the government of the world under one umbrella seeking the ban of bitcoin.