SEA, and SFO and most of the others have been done by Fly Tampa.
However they were for FS9 and are consider legacy products. New sceneries need to be done from scratch for FSX standards.
Totally agree! there needs to be a "Kick-A$$" Seattle update. Not only for Flight Sim X, but the 3rd runway, sound transit light rail system, No red watertower, more rental/parking garages (only one on Flytampa) Delta "S" concorse Upgrade (as well as NWA Hangar).