The U.S. Army is unlikely to increase it's size, given current recruiting problems. The army really doesn't want to increase its strength, knowing that each additional soldier will cost an average of $150,000 a year. The army knows that Congress is basically grandstanding by demanding that troop strengthbe increased, but will not provide sufficient money to maintain those extra troops in the long term. Thus the army will eventually have to cut back on training and new equipment in order to pay for the additional troops that are not wanted or needed.
To deal with the demands of Iraq and Afghanistan, the army is doing some long-overdue housecleaning. So far, about 40,000 troops have been shifted from support to combat jobs. This has caused some ill-will among some of the troops transferred, especially among female soldiers, who are not as keen on the "field army" life as are most male troops. But the army has not experienced any fall in re-enlistments because of this. Troops know, far better than Congress or the folks-back-home, that there is a war on, and that the army is winning it. While under orders to keep quiet about the "when will the troops return from Iraq" subject, planners can track the growth in Iraqi police and army strength, against the decline in terrorist attacks, and support. U.S. Army troops strength in Iraq will be declining soon, and the risks of being in Iraq are already declining. Thus by the time the army got any new troops, as demanded by Congress, it would have nothing for them to do.