Really can't see a guy like that going out with a loss. He'll be back.
My thoughts exactly. The dude is a competitor and I'm sure he not only wants at least one more chance at a Super Bowl, but not to go out with a Super Bowl *defeat* being the last taste in his mouth. That would be one bitter pill.
Then there is also the issue of making 11M, if I recall, to come back for 2019-2020 which also helps.
He is playing at an absolutely elite level, and at least from the outside looking in, appears to still enjoy the game, the brotherhood that exists in the locker-room, etc. Even with a notable decline in level of play, he would still be very competent out there. Importantly, his health seemed to be fine as well. If he wants to, I think he could even play another 5 years barring injury. Maybe not in the same capacity. But he's that good.