Apparently, King Abdullah of Saudi Arabia "read the riot act" to Dick Cheney when he was there last month (and not because they went on a hunting trip and Dick tried to shoot him).
Apparently, the Saudis are worried that the Americans will leave Iraq and are warning that if this happens, the Saudis will support the Sunnis; not Al Qaeda, but tribal groups. Iran, of course, will support the Shi'ites and of course, Iran and Saudi Arabia were never particularly close even when Iran had a relatively sane leader, so you can see where this is leading ...
The Americans, of course, say that the issue doesn't arise, because they won't be leaving. Bush has apparently rejected (or damned with faint praise) the ISG report on "how the F**k do we get out of this mess" and says he won't be rushed on developing his own policy. We're waiting patiently, because we know nothing could possibly go wrong with that.
So, what's next? Ultimately, America will leave Iraq, one way or another; maybe fighting will die down for a while and then flare up once they leave, as rival groups bid for power. The Shi'ites will probably want their own autonomous area in southern Iraq (which will border Saudi Arabia), the Sunnis there will fight that and ultimately, Saudi Arabia will end up at war with Iran. And that's not as bad as it can get, because the Kurds in Northern Iraq will want their independent homeland and the Turks will probably want to prevent that (and perhaps Iran and Syria too). So, all things considered, this has the potential to blow up into a major regional conflict ...