Exactly zero.
(1) Harbaugh is gone, so there's no point person to go after.
(2) Who/What is the governing body of NCAA football anymore?
(3) Penn State (albeit a weak PSU), Ohio State, Alabama, and Washington had the chance to do more damage to Michigan than any investigation result will do going forward. None were successful. Those game results are etched in memory. Reggie Bush won the Heisman that was eventually forfeited. Without looking it up, who was the runner up? Did they get the trophy after Bush's was vacated?