When he's good, Newton is a top 12 QB in this league. Sadly, Newton's last good campaign is 6 years in the rearview mirror. If Bill wants to ride him for lack of any other choices, fine. If Bill wants to stick with him even when they're mathematically eliminated, that'd be headscratching from afar, but ok, fine.
If Bill wants to subject us, himself, his staff, Josh, ownership, and the team to having this guy under center next year as well... that will truly test the In Bill We Trust mantra.
For what it's worth I don't think it comes to that unless he signs for 1M all over again (he won't, thankfully). They'll roll with a rookie or another reclamation project. There's no guarantee anything else will work out, but it's a damn near certainty that by this time next year, Newton will be putting the wraps on the 7th year since he was last any good.