I think you're missing the point. You can't give Monti "one more season" unless Gannon comes back because GMs don't get to go out and pick a whole new coaching staff only to be fired the next season. It's not what happens. So, if the thought behind the scenes is to give Monti a make-or-break year, you pretty much have to keep Gannon, which would be moronic.
Basically, the choices are to keep Gannon and Monti, fire Gannon but keep Monti long-term with a new coaching staff, or clean house. There's really only one sane choice, considering the current state of the Cards.