Franklin had reached his ceiling? We were a player's epic brainfart away from competing in the Natty game. I'll take that ceiling.
When Rhule took over at Temple, they had had one bad season ... he came in and made it worse before getting back (3 seasons later) to slightly above where they were prior, under the helm of uninspiring coaches.
When Rhule took over at Baylor, they had had one bad season ... he came in and made it worse before getting back to where they were prior.
When Rhule took over at Nebraska, they had had a ton of consecutive bad seasons under one awful coach ... he came in and made them mediocre (going from 4-8 to 5-7 in his first year ... woohoo!).
The point being, there's no indication from his decade+ long head coaching experience that he's going to do any better than Franklin ... likely, he'll do worse.
One huge criticism of Franklin has been his performance in "big games" and top ranked teams. Rhule has had equal futility, not just against TOP ranked teams, but ANY ranked teams. I think I read he was something like 2-22 against ranked squads all time. And I'm not sure if that was updated for this year, when he again hasn't been able to beat any ranked squads. They've never done anything in the postseason either - the one time in his career Rhule had a nationally relevant squad, not only did they go the whole season without beating a ranked opponent, they lost the conference championship game and the Sugar Bowl ... going 0-3 against ranked squads that year.
THAT appears to be HIS ceiling.
Except he takes a bit to get there, and it's likely his actual ceiling, going forward, is lower than that. His current Nebraska squad is underwhelming. There's no big breakthrough (season 3 or otherwise) likely on the horizon.