(OopslaProgramCommitteeMembershipPatterns)
Going from total immersion in a conference, to isolation from the conference, is good neither for the conference nor the chair. The chair accumulates a wealth of experience during her tenure, experience that should not go to waste.
The chair deserves a rest after a year of hard work on behalf of a conference, yet should be given a place of honor and influence in the successor conference: Many cultures find esteemed positions of background influence for leaders whose formal responsibilities come to an end.
Therefore: Invite last year's chair to a prominent position on the ProgramCommittee?. The former chair can advise the current chair in areas of the current chair's inexperience.
Chairs from prior years can add much to a program committee as well, as long as one can avoid the problem of too much leadership and not enough workers.
The authority of the current chair and wisdom of the immediate past chair come into balance under the mutual respect fitting their stations.
See also OldHandsAndNewHands.