So now that Iraq is on the verge of a civil war, what's the alternative?

Well, to re-unite, of course!  But re-uniting is easier when you share a common foe, in addition to having some latent affinity for each other.

So, there's hope for a united Iraq.  The Sunnis and Shias are re-uniting in Kut, after all.    According to CNN:

A similar scene played out in Kut, also in the south, where tens of thousands of Sunnis and Shias joined together Thursday, carrying the Iraqi flag and finding a common foe -- they chanted "No to America!"

On the other hand, if they want to unite against us, I say fuck them.  Just let them go at each other.