Update: I have confirmed this myself via SM as well:
DDF member mayer522 reports that he was told in a SM from Chase that Korean Airlines will be back as a Chase Ultimate Rewards transfer partner after a 2 month hiatus effective this Sunday, 01/25.
Thank you for contacting Chase about transferring points
to Korean Air.
Please note, for contractual reasons, Korean Air was
removed as a points transfer partner in Ultimate Rewards.
I apologize for any inconvenience caused.
However, Chase has renegotiated the contract for Korean
Air and it will return as a points transfer partner on
January 25, 2015.
If you have any further questions, please reply using the
Secure Message Center.
I have not been able to independently verify this, but Korean offers lots of sweet award redemptions that were part of the “30 awesome things you can do with Ultimate Rewards” so that’s great news if it pans out!