There should be an independent Kurdistan
An independent Kurdistan would cause war between Kurds and Turks, because a great part of eastern Turkey is dominated by Kurdish people. War would last at least three to five years, imo.
Ron Paul, a few months ago, advocated a federal solution (a la the original American constitution) to the Iraq problem. In other words, there would be three states, one Kurd, one Sunni and one Shia within the larger Iraqi framework. A central government would be located in Baghdad, but each region would have its own separate "state" government to handle more localized issues.
I find this to be the best solution, personally. Nonetheless, as of right now, the government will be Shia-dominated. The danger in this for America is the Shiites deference to Iran in the past. We'll see whether that continues.