mt best friend is a die-hard USC fan and we talk quite a bit about the reasons for USC's success. we consider leinart to be a "systems guy," like wuerffel (sp?) under spurrier or lefors under the petrinos. norm chow has his system, and it works, and it churns out quarterbacks with gaudy numbers. he did it at BYU with mcmahon, young, and detmer. he got (former new york giants great) phillip rivers started at NCstate; he's on it again at USC. quarterbacks become great based on chow's offensive genius.
without chow, USC's offense will begin to falter, as there is not an apparent replacement for a guy with chow's planning skills and ability to adjust, especially this late in the job-searching season. the trojan defense will win them a lot of games, and their offense has too much raw talent to lose consistently, but chow is a vital organ in the being of USC football. just like any other top-shelf program, they'll come back to earth without chow and put up 8 to 10 win seasons in the pac-ten but they won't be as dominant as they are now. without chow they'll be in florida state land: consistently good recruiting based on "prestige of program," and a conference that they'll easily dominate (like FSU before the miami ACC), but they won't necessarily compete for the national title each year.