They don't bring much as far as new territory or viewers though. Even Herman was complaining earlier this year about fan support at the games.
I doubt it, but I don't have a crystal ball. Urban is not going anywhere in the next few years. Greg, I'm assuming, will get an opportunity before the Ohio State job opens. When Urban does decide to hang it up, Schiano is only 2 years younger, so depending on how long Urban sticks around, it could age Schiano out of the window.
Either way, garyrc70 is right. Herman will get the first call. Maybe he's at Texas by then and he's settled, maybe there's a new hot coordinator who's come through in the meantime. Maybe Ash kills it and he gets the call...
We're probably at least 4-5 years away from finding any of this out.