You may not remember this specific piece of Cowboys trivia, but the last time the Cowboys changed their head coach after an 8-8 season, they ended up with a 5-11 record the next year.
Chan Gailey (trivia alert: Gailey was the only Cowboys coach to make the playoffs every season with his team) coached the Cowboys to 10-6 and 8-8 records in 1998 and 1999 and was then replaced by Dave Campo, who promptly took the Cowboys to 5-11 in 2000. Campo, of course, followed up that season with two more 5-11 seasons before he, too, was fired.