Campbell is a 5-time National Champion so I can see why the Jets would have interest.
In all seriousness, I don't know how much serious interest Campbell has. The Jets roster is pretty bad and they aren't going to draft the 'sure thing' pick in Lawrence. NY is such a volatile market that you could be gone in 2 years like Gase so job security is fragile compared to Ames where Campbell could have a job being .500 for the next 10 years. Conversely, the NFL is such a huge stage and NY/NJ is such a huge market that I get the incentives to want to take the jump.
Also, any Iowa fan who wouldn't be at least a little happy to see Campbell leave Ames is lying.