"Not sure where the Jan 2016 mention for Kelli comes from (source?), but I can assure you she will be with this show for the foreseeable future. I do know for a fact that she currently has no plans to leave the show or has a set date. "
When I emailed Lincoln Center Theater, a marketing assistant wrote back that the original contracts for both were through July 5th, the last date for which the original block of tickets was put on sale. She hadn't heard yet about extending the contract.
I guess since it turned out that Ken's original contract ended on July 5th, you might infer that Kelli's extension would end in January on the date of the end of the second block of tickets.
It's always seemed to me that doing the same performance eight times a week for month after month would get tedious. Apparently not. Something about "every performance is different."