You can do all the contingency planning in the world, and tell all the good coaches in the country that you'd like to hire them the next time to job opens. But none of them can make any substantive promises that they'll sign on the dotted line when that day comes. The only thing they can really promise is that they'll give it serious consideration and won't let contractual obligations at their current job get in the way.
Jack will never disclose the extent of contingency planning he has done. If the first guy he offers the job to says "no", then a lot of people will claim it as proof that he didn't plan ahead, but that just isn't necessarily the case.