The precedent is set that the NCAA rules in an arbitrary fashion. At OSU Troy Smith won the Heisman, at Alabama it would have cost the team 20 scholarships and Maurice Clarrett would have gotten the program the death penalty.
As a USC fan, you have nothing to worry about. The NCAA has no agenda against you so the school will not be affected.
In 1997, Michigan's Charles Woodson won the Heisman Trophy and Michigan won the national title. It was shown several years later, in 2001, that prior to and during his Heisman year at Michigan, 1997, Woodson took money and other benefits from Summit Management, a sports agency. Auburn's All-American Victor Riley was also shown to have taken cash, and a third player, also from Auburn, running back Stephen Davis, admitted in an interview that he took cash from Summit while at Auburn.
NCAA spokeswoman at the time Jane Jankowski said that accepting such benefits while competing would violate NCAA rules, but that the NCAA typically does not investigate such cases after the player has left the school unless there is blatant evidence that university officials knew, or should have known, about the violations. "We don't see any evidence of that" Jankowski said. Jankowski also said the NCAA would have no power to revoke Woodson's Heisman Trophy.
So first of all, apparently Auburn is on the 'favored list' as well, because I don't recall seeing any Auburn games forfeited due to the actions of these two players. Secondly, if USC didn't have any involvement or knowledge of Bush's step-father's shenanigans, this is a pretty close parallel to the Woodson case. Michigan still has their wins and their title, Woodson still has his trophy.