The official Holiday season in DLR ends on January 6 (Wed). If you go before that, there will probably be very large crowds in the parks.
The Rivers of America (Mark Twain/Columbia, Canoes, Tom Sawyers Island, Fantasmic!), the Train, and the Big Thunder Ranch and Petting Zoo are slated to close permanently at the end of the day on January 10, 2016 to make way for Star Wars Land. The Aladdin musical in DCA is also closing on Jan 10 to make way for a new Frozen show that will debut in the summer. IaSW, Jungle Cruise, and Haunted Mansion are likely to close at some point in January to have their holiday overlays removed. Typically (last year was the first year), Jungle Cruise closed right after the Holiday season ended. HMH remained opened through the weekend and then closed to have the overlay removed. IaSWH closed a bit after HMH re-opened to have it's overlay removed. Generally the water attractions (Splash and GRR) close at some point in the winter for a refurbishment. Other than the water rides and the rides with holiday overlays, it's hard to know what will or will not be closed. DLR does not follow a set/predictable pattern of closures for the most part.
At this point, no one knows what the non-peak season entertainment calendar will look like after the Holidays end. Normally, fireworks would go to a weekends (Fri to Sun) only schedule, but they presented fireworks nightly during the current non-peak season (Labor Day to the start of the Holiday Season). That being said, I would plan for fireworks to only be offered on weekends. WoC should still be presented nightly. It's been a long time since DL had a nighttime parade, so it's hard to say whether PtN will be nightly in the non-peak season or not.
I recommend checking out
HydroGuy's Detailed Weather Data for DLR thread.
I don't have a lot of events listed for 2016 yet, but the
2016 Calendar of Events & School Breaks and DLR thread has some information.