Not a fan of Dennis Dodd, but in this piece he gets at the reason why Kelly might well leave--he was lucky as heck to go 12-0 this season and will have a hard time replicating the feat:
http://www.cbssports.com/collegefootball/blog/dennis-dodd/21534588/kelly...
"[D]on't interpret Kelly's interview with Philadelphia as a “money grab. . He is/was going to get paid," Dodd writes. The reason why Kelly moved fast: "The bar has been set for him and his program. There is no going back. . . Ten wins won't be acceptable, probably not after this season. . . at the moment, there is more certainty that Kelly can get himself to the next level (NFL) than he can keep Notre Dame at its current level."
Anyone disagree with this assessment? Seems about right to me.
Mod Edit: thought Kelly had decided to leave based on title. Edited said title. [zl]

and then at ND's future schedules(ACC) I would say that Kelly is on track to a sustained run of success at ND.
That said, Kelly, like most coaches, has supreme confidence in his abilities. If he goes to the NFL it is because he wants to prove that he can win at the highest level in football. It isn't about money, but ego.
"The Ruhr will not be subjected to a single bomb. If an enemy bomber reaches the Ruhr, my name is not Hermann Göring: you can call me Urban Meyer!"