There was a plan to encircle Baghdad and slug it out maybe even fighting in urban Baghdad. Given that scenario I would Imagine that the military had planned for 2,000 to 3,000 deaths even before Baghdad was pacified.
The commanders on the ground saw an opportunely and Franks allowed the "Hail Mary" dash into Baghdad and by May 1, we had Baghdad with only 138 dead.
Had things gone by the plan I believe that we would have had 2-3 times the numbers of death that we have today.