The forecast, as of now, looks grim. This could be the storm that gives FEMA planners nightmares.
If the forecast verifies, New Orleans may not exist come midweek. The city is essentially a bowl that is sinking under its own weight, in addition to the encroachment of the Gulf and the fact that the Mississippi is ready to shift westward to a new mouth, but can't because the Army Corp has channelized it. I wrote a paper about this very scenario a year ago.
It should also be noted, that the Gulf Coast of Louisiana and Mississippi are covered with refineries. If the forecast verifies, expect a severe increase in prices over the next few weeks.
And...the atlantic is not done. Peak time for the Hurricane Season doesn't occur for another 12 days.
You can watch coverage of the evacuation of Southeast Louisiana here.