if all the governments of all the world joint hands together to banned bitcoins ,then only would bitcoin can come to an end.otherwise it is not gonna happen no where soon. because of its decentralization and no technology could beat because it is the first of its kind.
Even if the government do ban the bitcoins yet how can they stop user's from it's trading ? I mean I can tell you any countries where the government does not appreciate or allow bitcoins transaction yet people are doing them quite happily.
The network is made in such a way that if a user is educated enough about bitcoins then he can use them in a totally untraceable manner.