Now that he has his contract to pay him more money than he needs to live the rest of his life he has even less reason to change.
DING! Winnner! As I said the day the Bears signed Cutler in the first place, he'll never be anything other than a low to mid-tier QB in the NFL, and on most teams would never have been the starter in the first place. Once they get the big guaranteed contract, they're set. They're done. No need to risk getting hurt and playing hard.
You're exactly correct that signing the big dollar guaranteed contracts almost always takes away the incentive for a player to continue to perform at a high level.
Flacco (Ravens) and Manning (NY Giants) come to mind. As does Jared Allen who the Bears acquired from Minnesota this year.