During my research, I obtained a copy of Will's contract for the appearance.
Along with the usual cancellation stipulations and hotel requirements -- as well as his $48,000 fee -- the contract stipulated he could pull out of the event without penalty if the Chicago Cubs had made it to the playoffs or World Series. An Illinois native, Will is the author of several books on baseball, including one on Wrigley Field (at left), the Cubs home.
See the relevant portion of the contract below:
Of course, as anyone who follows baseball knows, the Cubs have not been in the playoffs very often, including this year. So Will's calendar appears to be safe from disruption.