Here's what I know.
Grew up an Auburn fan and I still have a ton of connections in the Auburn program. There is a ton of mixed emotions about Chizik in the Auburn community. There are some that still have the high from the National Championship, then there are some that see the discipline problems and think Chizik is incompetent. Firing him after a losing season would piss a number of people off, but I don't think that number would be enough to prevent Auburn from actually doing it if they chose to go that direction.
The interesting part of all of this is the PlaneGate as Auburn fans call it. Everyone knew Auburn wanted Petrino and wanted Tubs gone, and Auburn fans knew they had been in contact multiple times during the season and during the offseason, yet they placed little to no blame on Petrino. They were pissed off at the administration involved once this all got leaked to the press. Petrino survived that situation, the Falcons incident, and the motorcycle ride at Arkansas with many of the currently pissed off Auburn fans believing he is still a viable HC candidate.
I don't believe your situation is too farfetched, mostly because everyone knows Petrino is a damn good college coach, he's been at the Auburn program before, and many of the higher ups at Auburn during PlaneGate that wanted him are still actively involved at Auburn. Auburn is a high profile enough university to survive the public backlash they would receive from this, and I can't blame them for hiring Petrino if that's what they choose to do.
I will also add that after watching Auburn Saturday night, them going 6-7 is very much within the realm of possibility. They already lost to Clemson, and they should lose to LSU, Arkansas, Bama. Throw in games against us, TAMU, UGA, and an improved Vandy team in Nashville, and they have a ton of opportunities to mess up.