I'd bet the MK will be down by 1/5 (marathon is on 1/7-8 and they are usually down when the marathon comes through). Same with most of the other parks. Resorts will start coming down about then, but might still be up until 1/8 or 9.
It has varied over the years, although since the Osborne lights came to Disney/MGM, the time has been extended both earlier in November and later in January. However, I notice that the official Disney site only has the Osborne light listed through December 31st, but that could be becuase the calendar only goes up to that date. We did see the Osborne lights up as late as January 10th back when they were new to the park.