I was at NYE in 2014. MK closed at 11:00am on Dec 31st. We saw the fireworks on Dec 30th and stayed til park close. After the fireworks the park emptied out, but the fireworks were at midnight and I don't believe the park was open to 1 or 2am.
On the 31st we hit MK for morning EMH and did some attractions, but when I encountered a line for the Starbucks that snaked down Main Street, into the little side street, past backstage door there, and ended in front of the SotMK window there I figured we should get the heck out of MK, so we hopped to DHS for evening festivities and champagne. We had a blast there, but taking the bus back at 2am was crazy.