Well, if history holds true and it carries over to this season (which is unlikely with the experience and talent that the Seahawks have), no Superbowl losers have put up a .500 season the year after. It's true for the 2001 Giants, 2002 Rams, 2003 Raiders, 2004 Panthers, and 2005 Eagles.
This could be true for the 2006 Seahawks. The last team to put up a .500 season or better after losing the year before was the 2000 Tennessee Titans after losing to the Rams in the superbowl and putting up a 13-3 record the following season.