Source: Associated Press

I don't think it's fatigue that prevents a memorial, I think the city just isn't ready:

New Orleans has seen an estimated 67 percent of its population return since the 2005 disaster that submerged 80 percent of town. But government statistics indicate many are not original inhabitants, with up to 200,000 pre-Katrina residents forwarding U.S. Mail to other parts of the country a year after the storm.

With the dislocation, there is no organized group of surviving family members to push for a memorial, as was seen after the 2001 World Trade Center attacks. Residents and activists have focused on the challenges of the living.