Would it have made sense to replace Eisenhower in early 1945 or Grant in early 1865? Only someone who thinks the answer to those questions is "yes" would be in favor of replacing David Petraeus as the senior commander in Iraq anytime soon.
It's a bit of an exaggeration--our enemies in Iraq are hardly on the brink of unconditional surrender--but the point stands. Here's Boot's recommendation:
It would make more sense to send Petraeus to Central Command, replacing the unimpressive Admiral Fox Fallon, and thereby allowing Petraeus to stay involved in the command loop not only in Iraq but also in Afghanistan as well. As for his replacement in Iraq, who better than Odierno, after he has a chance to rest and recharge his batteries stateside? That would keep the winning team together.
That would seem to make a lot more sense.