If he wants to leave for more money, the offers may come, and we may or may not be able to match. He hasn't yet, which is a good sign. If he wants a program with more built-in advantages, the offers will come, and we can't do a whole lot about those except try to keep improving.
If he wants to build a program and make it his own, not just take over where someone else has already succeeded over the last 20, 50, 100 years, Iowa State is a good place to be. If he wants to have a job where he'll have a fanbase that, with a little success, will give him all the patience in the world, and not fire him after one bad season, ISU is a good place to be (look at KF's job security). At some point with what he's making now, he's living pretty damn comfortably wherever he goes.
Ultimately though, its going to be a decision he and his family make, so its pretty pointless to keep worrying about it without a credible rumor that someone has come calling.