Well, i'm fully in the belief of there being a dispute and war breaking out... Not any war, yet a nuclear war the has the calability of completely wiping out the human race.
Now, for sure there will be something in the future referred to as 'The Oil Wars'. These wars will consist of China, Northern America, Russia, and any semi-wealthy European country to fight over the last of the precious oil (sometime in the future).
Lastly, as you might know, the world is already overpopulated. Countries such as china with about 1415 people per square kilometer will of course be struggling with the overpopulation... Human eradication and other ways to put down population. The United States, having the nature to make everything their business will jump in and start WWIII
Those are my possibilities.