A lot can change between now and training camp, especially if a guy like Polian's back in the mix. There'll be an Orton-level guy (or even slightly better) shake out somewhere, even if it's not apparent who that is today.
The way I see it, Marrone came from running the whole show at Syracuse and never seemed to accept that he was only one voice in the management structure at OBD. If Polian comes back, Marrone's input is that much smaller.
If he goes to the Jests, I can see him convincing Woody Johnson to give him more control over the entire football operation. That, and that alone, may have been enough to cause him to pull the plug...