I don't think he's truly on the hot seat until next year. Coaches who can win NY6 games are worth giving a longer leash to, and a lot of our issues are correctable. But I can't say I'm confident he'll do what it takes to fix the coaching issues at this point.
He does do a lot of things well. His recruiting and development has given us our most talented teams in my lifetime, and that's probably the hardest part of the job. The defense is elite, and while you can rightfully give Heacock a lot of credit for that he's probably only staying on staff with Campbell. The odds of getting a good developmental coach with a great defensive scheme that won't bolt at the first sign of success are very, very low.
But the offensive scheme is broken, and it doesn't look like we're trying to fix it. Campbell and the staff actually have completely reworked a scheme and had success with it, they did it mid-season in year 2 with the defense, but for whatever reason he's unwilling to try that with the offense.
He's also a terrible game manager, which is really the easiest part of the job. Just hire an analyst, play some Madden and figure out what works, or just go with the more aggressive option every time since that's usually correct. Even notoriously stubborn Kirk Ferentz has significantly improved at it since his early days. Just stop playing not to lose.
TL;DR I think this can largely be fixed if he stops being stubborn, but I'm not seeing any sign that's coming soon.