I think it would take a hell of a lot for him to leave voluntarily.
He loves the club and the town. Stockport is his home and has been for pretty much his entire adult life. He gets the town, he gets the club. He is one of us, a Stopfordian, a County fan. He wouldn't have that elsewhere.
That relationship also affords him some extra slack from the board and fans he wouldn't be allowed the time for elsewhere.
I firmly believe he wants to create a legacy here. That he wants to be our Alex Ferguson/Brian Clough/Dario Gradi (minus the bad stuff of course) With young players coming through, playing good clean passing football. Taking us back to at least League One, if not the Championship (where we were quite possibly headed before things went bump in his first spell).
He also has a young family settled here, would he uproot them for a possibly precarious position?
He's tried managing elsewhere before, and discovered the grass isn't always greener (granted that'd when he's been pushed out of County). Why go somewhere that might want a quick fix and will let him go in 6 months, a year if things don't work out, when he could stay here and build a real legacy for himself and the club?
That's not to say that a Board or owners might decide to let him go. But I think it would take something almost unbelievably special for him to leave voluntarily.