How likely do you think it is that the world will see a straight up war between Shi'a and Sunni in the middle east.
War in Syria
Increased tensions and attacks in Lebanon
Increased tensions and attacks in Egypt
Attcks in Iraq
Sunnis (Qatar, Saudi Arabia) funding one side
Shi'a (Iran, Syria gov.) funding the other
That would be the most stupid war of the history, even more stupid than the Honduras-El Salvador war.
However, I don't think it will be(a straight up war), because the current situation (all the strifes and conflicts) are much better for all the parties' interests, even for themselves. They, Sunnis and Shia, do not want war as well as they do not want peace either.