Iggy’s game is already very mature, little benefit of staying longer. I think 15-20 is where he can go.
For his long term success, Yaklich needs a plan for offense besides his defense. If he is level-headed, he will stay with Beilein for a few more years to learn from the master. That’s why I don’t see him leave right away, but he will make himself ready after another 3 years when the opportunity knocks.