By the time the missing FR would have been juniors ready to play on the OL, USC will be off probation and they can take juco transfers that walk in immediately ready to play. They will step straight into the Jr class as men and finding OL via that route isn't hard.
USC lost what they needed to be top 5 in 3 or 4 years today, but they can easily fill holes on the fly via jucos to prevent falling out of the top 25.