I think you're right. Marshall wants a superbowl. If Cutler leaves than the QB is the most unstable position and he doesn't know if they drafted the next Luck or Gabbert and there's alot more shakyness. He sees the team getting older the defense diminishing he may be looking elsewhere to a more stable team not a rebuilding one.
Aside from deciding on Cutler's fate with the team, it's also probably a decision on whether or not the Bears go full rebuild or try and patch together the defense enough to possibly contend for a championship in the next few seasons. If Cutler goes, it's probably a full rebuild. Names like Hester, Briggs, Tilllman, etc. will most likely follow him in departure. There are other players on the fence that you have to make quick decisions on. Marshall is 29. Willing to bet he can hang on physically after a 2-3 year rebuild? You could even question the merits of shopping Forte, who'd be on the wrong side of 30 for a RB after the rebuild gets done.
Trestman has to be aware of this too, I'd think. If the Bears keep Cutler, he's got 2-3 years to turn him and that offense into a unit worthy of title contention, or he'll be leading the rest of them out the door in 2-3 seasons, provided that they don't start winning more. But if he commits to a lengthy rebuilding process, he could probably argue for a bit more time to develop the team.
