If we're not counting stuff like the Kosovo conflict as a "war" from the US side, then it'll probably happen as soon as the US withdraws from Afghanistan.
Assuming the U.S. has withdrawn from Iraq before withdrawing from Afghanistan. When do you think the U.S. will withdraw from both those countries?
According to the status of forces agreement, the US is supposed to withdraw from Iraq by the end of 2011. Even if that deadline isn't met, the number of remaining troops and the scope of their mission will be narrow enough that it won't count as "fighting a war" any more than the US mission in Somalia from 1992-93 was "fighting a war".
With Afghanistan, I really have no idea. Obviously, it will continue beyond 2011. Beyond that, I don't know. That's why I started this thread:
https://uselectionatlas.org/FORUM/index.php?topic=117627.0
