Some points to consider:
-- As of today, Bo and Tressel's contracts expire after the 2014 season. Tressel will be 62 then.
-- In 2014, Bo's children will be 16, 14 and 12.
Hypothetically, if Tressel retires after the 2014 season and Bo is offered the job, the only thing that might prevent him from taking it is his children. Bo and Pat would have to ask themselves if it'd be worth uprooting their children out of Lincoln, specifically the 16 year old who would be a Sophomore in HS. The children will have developed a 7-year bond with their friends and community. If any of you recall what you were like from the ages of 12-16, you'd know those are crucial developmental years (puberty, etc.) especially physically and emotionally. Pulling them out of Lincoln during that stage of their life (especially the 16 year old) might not be worth the risk?
Either way, I wouldn't be surprised if Bo took the OSU job in the future, but at the same time I also wouldn't be surprised if he turned it down either. It's not uncommon for college coaches to turn down opportunities to coach at their alma mater. Les Miles and Kirby Smart are recent examples. In Smart's case he was offered the DC position at Georgia, and they were willing to make him the highest paid assistant coach in college football but he turned it down.