We are booked on the Dec 17th cruise on the Granduer. I just called RCCL (both existing reservations and new bookings) and they said New Orleans is still the departing port. The Mississippi river is open and is restricted to ships with a draft of 35 feet of less. Currently a 900 foot US Marine Corps Helicopter ship will be using the Julia Street Cruise Terminal to launch rescue missions.
A lot can change between now and Dec 3rd (the first departure from New Orleans.