The six-place sedan is coming very close to joining the Passenger Pigeon. Anyone younger than about thirty years old isn't likely to have memories of straddling the transmission tunnel in the middle of the front seat, trying to keep knees out of the hungry teeth of radio pushbuttons or HVAC controls.
In an opinion piece for the Detroit Free Press, Mark Phelan ponders this phenomenon, and notes that big coupes have already gone extinct, with General Motors seemingly providing the last gasp of each format. There are several reasons for this; most mainstream sedans have transverse-mounted powertrains and front-wheel drive, which means no hump to straddle. And with the death of Ford's Panther platform, there's only the 2011 Chevrolet Impala available for buyers seeking a front bench seat and six-passenger capacity in a sedan.
The attrition is mostly due to changing consumer tastes. While bench-seated sedans were once the kings of the road, car buyers have found better solutions for moving a sextuplet of people. Jim Hall of Michigan's 2953 Analytics notes that baby boomers "didn't embrace their parents' sedans," preferring instead to go for crossovers and minivans.
The change in buyer preferences, and the fact that a sedan is about the most uncomfortable way to transport six people, may spell permanent doom for the six-seat sedan. It's not going to surprise anyone if the 2013 Chevrolet Impala has a center console and no optional bench seat... and it's not likely anyone will miss it.