I'm afraid that if action is not taken SOON, like getting them out or using some massive pumps, they will drown. Disease is going to be more than rampant.
The folks in the Superdome will not drown. I don't have the exact height numbers, but the building sits up on a concrete platform, so even if the streets around it flood much worse than they are now (2-3 feet last I heard), they'll still be dry. Now that doesn't help people that may be stuck in other parts of the city...we have to pray that the water rises no further, that Lake Pontchartrain has drained all that it's going to drain into the city, and that the levees on the Mississippi River (which is considerably higher than the lake) hold and don't flood the city from the south.
}:-)4
They are saying on CNN right now that pumping will not do much -- considering breaking down some levees that protect the city from hurricanes to allow the water to drain out.