US will never pull troops out of Iraq - at least not completely. US did not go into Iraq to create the largest US embassy in the world in Iraq and then leave it empty.
The plan is a strategic 'We Stay for ever' and control the region. They will play the political mind games for as longs as they can with - they are only under a little pressure now since the Occupy Wall street movement is gaining momentum and if it continues then you will see BO declare some solders will be taken out but a huge number will remain.
There is nothing stopping BO from pulling all US troops out of Iraq over the next 6-12mths (the excuse of Iraq being unstable is just that an excuse) the country since the occupation has never been stable and it will never be stable until the Western powers stop meddling in other peoples affairs for petty gains.