On November 6th-8th, 2015, D23 Expo Japan and Square Enix released an extended trailer for Kingdom Hearts 3. However, the trailer was never released online to the public and was only screened at the expo. According to eyewitness accounts, the trailer featured an extended conversation between young Master Xehanort and Eraques, more attraction flow rides, new features in the "Tangled" world, new heartless and nobodies, and an "emotional" ending. Only 2 screenshots have been released after the expo ended.
On December 13th, 2015, six seconds of the trailer was leaked online from a re-cap video of the expo by the YouTube user, "I Love DCS JP". The six seconds shows Sora, Donald, and Goofy in the "Mysterious Tower" world riding Buzz Lightyears' Astroblasters and/or the Toy Story Midway Mania! ride.
On December 18th, 2015, the trailer was finally released to the public during Jump Festa 2015, a gaming expo in Japan.
http://s3.amazonaws.com/katsunews/e3fcac3a-e347-4afd-984a-beb00eea533c.jpg
Link to the re-cap video (go to 1:29):
https://www.youtube.com/watch?v=A-8B4bvenhA&feature=youtu.be&t=68