NHC is currently calling for a 140 mph category 4 landfall in Louisiana on Sunday. That's one of the highest forecasts I've seen from them this far out... but a lot of the statistical model guidance is off the charts right now. Cat 5 is definitely not out of the question. I would evacuate if I lived anywhere in southern Louisiana including New Orleans.
If Ida passes west of New Orleans, weirdly enough it probably works out better for the city The right side of a landfalling hurricane has higher winds than the left side (since the counter-clockwise circulation combines with the storm's forward motion), which would mean a higher surge... except that New Orleans primarily floods not from the ocean, but from Lake Pontchartrain on the north side of the city. A track west of the city would mainly push water in the lake away from the city, which would decrease the Katrina-like surge threat a bit... but would also mean a greater wind and tornado threat.
Camille and Katrina both tracked east of New Orleans, while most models currently have Ida tracking to the west. Obviously that's not to say New Orleans is in good shape if that verifies, but it could be worse.