NO will rebuild on higher ground. Bourbon Street will be back with the bars, jazz and Mardi Gras. It will be cleaner and fresher but retain it's old NO charm. That's my prediction.
After the devastation of the 1900 hurricane, Galvestonians with turn of the century technology, built a 17-foot seawall and raised the entire city five feet in elevation. Another major hurricane hit in 1911 but a few hundred died rather than the thousands of 1900.
I think Louisiana would be well advised to rebuild the metropolis *north* of Lake Ponchartrain around where Hammond or Covington is now but those who see romance and culture as New Orleans' legacy will not allow that.
So perhaps the best solution is to bulldoze the entire city (yes, I'm serious), fill it with silt and debris then rebuild it ten feet higher - above sea level.
It would take 1-2 years at best to begin making it a liveable city again but it would prevent the levee-breaking disaster we are witnessing this week. New Orleans would have a much happier long-term prospect if such a plan was done.