I'm guessing by true wagon you mean a full-size wagon? Because there have been plenty of wagons since the Magnum was discontinued 14 years ago. Volvo V60 and V90. Mercedes E-Class Wagon. Subaru Outback. Audi A4 and A6 wagons, Golf Sportswagen etc etc
If you mean sold by an American company, then the Buick Regal TourX fits the bill, as far as being sold since 2008.
While I totally agree with your take on SUVs, myself I would much rather have a wagon and I do own a wagon now and plan to in the future, but there are wagons being sold in the US.