Honestly, in his place I might consider retiring even if a new contract is offered.
When I was younger that thought would have never crossed my mind.
Now though I think, the man has a superbowl ring and if he has been decentley intellegent with his money he has multi generational wealth. Football is physically demanding, and the strain of maintaining his athleticism at his weight, and the general wear of being in the trenches can seriously impact long term quality of life... and then there is CTE or the risk of serious injury.
He is also reaching the age, post prime, where maintaining his level of play will take more and more work for less return. He also has 3 kids, one of them 1yr old... he can see the world live it up, find and pursue other passions.
Now competitive fire in athletes of his level, undoubtedly tens of millions to be had in another contract, and the chance to build on his legacy probably keeps him from walking away... and this is probably just "public negotioation", but I would not be shocked if he walked away and even if he was a Saint I would not begrudge him that choice.