I don't see Saddam committing suicide. I expect him to try to broker a deal once he is convinced that the invasion is underway or nearly underway. If he waits too long he will not be able to deal and may get tried as a war criminal for past acts. The other cases are he gets taken out by his own inner circle. Finally, he could be killed in the action if it is prolonged. The logical place for him to go is Syria.
I would be in favor of such a deal to save the lives of our troops and the Iraqi civilians that will no doubt die if they lay siege to Baghdad and take out the power, water and sewage systems as well as cut off the any fresh food.
Is his ego large enough for him to commit suicide? Hitler's ego was big enough. I doubt that Saddam will commit suicide.
The bottom line is that there is a 50/50 chance for a deal before the outbreak of the battle.
So this could have a sudden impact on the market anytime before the battle begins.