This must be imagination time because there has never been one religion and if there were people being people would fight it and a large government plus like all large empires it would collapse under the weight of its own inadequacy. Every empire falls and there are always splinter groups in every religion so NO IT WOULD NOT because it is not possible unless people change and people haven't in 1 million years so why start now?
If there will be one world religion it will be Islam. Islam is at least 5 times as ambitious as Hitler ever was because orders come from a holy book instead of a person. They have a fair chance at succeeding too. The religion is subversive not only to government but even to human nature. Its the most formidable foe America has ever faced and IS a threat to our constitution in a way no conventional army could ever be. If secularists don't tear the reigns from the hands of the incompetent it is inevitable that we will be an Islamic country. Our atheist are strong because we deal with theism regularly but it may not be enough to combat Islamic terrorism. My bet is that we lose, Asia claims the globe. The cancer of theism has decimated America and it will take great strides by atheist to recover and bring America back to respectable status. But for now this mostly fat, mostly religious, mostly violent herd of people cattle are just the current occupants of this land to Islam. The religion of conquest knows exactly how to beat us and I don't think enough will wise up to there strategy and tactics quick enough.