What they're planning definitely won't be expected. Everyone will be surprised. And the outcome will be just as quick and decisive as Afghanistan.
Maybe not as quick but certainly as decisive. If our troops are equiped to deal with the chem/bio weapons Saddam has (which they will be), they'll have little trouble penetrating the interior of Iraq and encircling Baghdad. Once there and after utilities are cut off as well as food and supplies, they can establish refugee camps outside the siege and encourage Iraqi civilians and troops by radio, PA and leaflets, to abandon the city to save their own lives if not for other reasons they would already have.
The fear is that loyal Iraqi units, particularly the Revolutionary Guard, would prevent the populace and the garrison from leaving and that the UN would then insist on us going into the city to prevent a humanitarian catastrophe. My hope in that event is that a military uprising within Bagdhad would prevent that necessity. Absent that, we can expect to lose a lot of people in the action.