Who said anything about blowing up the NFL's business model? If the NFL can push back the draft some on a 1-time basis, change training camp start dates, but still begin the preseason and regular season on time, they'd explore that (and the potential financial ramifications). If the NFL can exert pressure on the NCAA to have its football season finished by early March (potentially with a half Fall, half Spring set up) they may well do that.
The NFL will do what it believes is in it's best financial interest. But the League absolutely wants college football to proceed as usual.
As far as sitting out, it is one thing to sit out when you are a projected 1st/2nd round pick. It is an entirely different animal for the majority of players who are still counting on this season to prove themselves and move up improve their resume for NFL teams.