Islam is the dominant religion. Catholicism isn't considered Christianity by most Christians and they only make up 17.4% of the world population, where as Muslims make up 19.2% of the world population. Similarly, Catholics have a total of 1.2 billion adherents, while Muslims have already surpassed that number with a total of 1.6 billion adherents.
Also, Islam is the only religion growing faster than the world population and is, in fact, the fastest growing religion, both by breeding and conversion. This is awesome because:
-Islam is literally the way of life for every human-being and Muhammad's example is the best model for proper living.
-The world will be following the true God and every believer will be equal.
-There will be peace, prosperity, justice, pluralism, and equity (just like the Pax Romana during the Roman Empire).
-There would be no more wars. Religious and political wars (i.E. War in Iraq, Israeli-Palestinian conflict) would end.
-There would be no more racism. Islam unifies people of all color, race, nationality, etc.
-Shari'a is ingrained in Abrahamic culture and the three Abrahamic religions (in their true aspects) worship the same God. Thus, Jews and Christians would be following something relatively similar to what they usually practice.
No, Islam is not our future, because there is enough room in the world for diversity. There are so many people in the world, it is unlikely that one religion will ever dominate completely. In addition, in the United States, the vast majority of people are still Christian. This might not be apparent with a loud majority, but Americans are still a very conservative Christian people, and this is not something that can be undone casually.
The humorous implications of my headline suggest how seriously i take religious arguments: NOT AT ALL. Any religion what preaches peace yet has organized violent groups in them is beyond failure, if you will failure^2! (exclamation mark being a mathematical principle).
But no, if history has taught humanity anything is that there will never be one divine ruling group/person/nation of this world...Even the Chinese PLA army.