I don't think that'll happen. Realistically, the legislature is going to have little control over what happens in Iraq. If the president decides that he wants to keep all the troops there, then they're gonna stay. The only real thing they can do is refuse funding, and nobody is gonna do that. Other than that, they can try and exert political pressure, but I doubt that'll do much.
Ultimately I'm concerned what effects that'll have on the democrats in two years. They won in large part due to Iraq, if things keeping going over there as is, then they won't be in as good a position to use it and it might work against them.