Three of the theme parks are celebrating New Year's Eve with fireworks: Epcot, Magic Kingdom, and Disney's Hollywood Studios. However, the
Park Hours for that evening are not yet showing all of the details for each park. Last year, Epcot showed Illuminations at 6:00 PM and 11:40 PM. The Magic Kingdom had Fantasy in the Sky fireworks at 11:40 PM. Disney's Hollywood Studios had Mulch, Sweat, and Shears! ringing the New Year with a show that began at 11:40 PM.
I can confirm that this year Epcot is having a New Year's Eve Countdown Fireworks that begin at 11:40 PM; Disney's Hollywood Studios is again having New Year's Eve Fireworks featuring Mulch, Sweat, and Shears! at 12:00 AM. As for the Magic Kingdom and other events at the parks, I'd continue to check the above link to see updates as they are posted.
New Year's Eve in the parks can
very crowded, especially the Magic Kingdom. However, with the recent renovations to the hub area in front of Cinderella's Castle, there is a lot more room for guests. This summer we watched the fireworks from behind the castle by Gaston's Tavern and found very few guests there, so that might be an alternative area to watch them. Epcot has a lot of celebrations throughout the World Showcase during the evening and does have more space for guests, but it will be equally crowded. If you'd like a glass of champagne to ring in 2016, this park is a good match. Disney's Hollywood Studios is also a lot of fun with more a "concert-vibe" with Mulch, Sweat, and Shears! performing, but the gathering space isn't overly large for guests. To read about more options, I'd encourage you to do an internet search for
Tips for New Year’s Eve at Disney World By Tom Bricker for a more detailed article and pictures from last year's New Year's Eve.
Wishing you a Happy New Year!