While I like Cam and am rooting for him, I don't know that the Panthers are going to regret the decision. As the saying goes, there are a lot of young running QBs but not a lot of old ones. And Cam is on the wrong side of 30. With all the retirements, I can see the club deciding to hit the total rebuild button. They're probably 2-3 years away from having another playoff caliber team, and at that point they'd probably be hitting diminishing returns with Cam. There will be 2-3 QBs in next year's draft that will be regarded as franchise QBs. Makes some sense to go after 1 of those 2 (they should have a high enough pick) and have Teddy mentor that guy for those next 2 years - which is the 1 aspect of the position where he'd be better than Cam.
And next offseason should be interesting again for the QB position because Cam, Aaron and maybe Stafford will be on the market. I'm betting that Detroit sucks again, and they can both the GM and coach and go total rebuild, which would mean getting what they could for Stafford.