I would ask him how feels and see if he really wants to be alone or what. If it were me, I would put the date off until a later point. The holidays are bad enough, but when the one you love is thousands of miles away for an extended period of time, and you're in a new place, it doesn't make for the best holiday season. Maybe you and your partner can go on a date before you leave.
Perhaps you can cut the date short or have a lunch date with the lucky person. Do what feels right in your heart. I know I wouldn't be able to enjoy if my DH was at home and feeling sad. Good luck with everything, and fingers crossed for a successful date--whenever it happens!