Steve Clemons brings some RUMINT regarding the possibility of a 2012 David Petraeus presidential campaign. This is something that strikes me as plausible if and only if my pessimism proves unfounded, and a Democrat takes office in 2009 who does withdraw American troops from Iraq. That would lay the groundwork for Petraeus to play the Hindenburg role in a stab-in-the-back campaign in 2012 (see, I'm not comparing my political foes to Nazis just to, um, soft-on-Nazism nationalists) in case anything sufficiently bad happens in the world to make such ex post facto carping compelling.
It does seem to me that based on the experiences over the past 15 years or so with Colin Powell and Wesley Clark that something about the modern officer's corps generates high-level personnel who don't really have the right personalities to be effective in politics. Powell unsuitability for a major political role didn't, of course, actually stop him from becoming Secretary of State, but it does seem like a cautionary example to me. On the other hand, even if Petraeus hasn't been very successful at improving conditions on the ground in Iraq, it's undeniable that he's turned MNF Iraq into a formidable PR machine reminiscent of its 2003 condition despite having fallen into considerable disrepair over the years.
At any rate, I suppose that's enough idle speculation for now, but it's certainly something to chew on.