Yes, thousands and thousands of people go to the MK on New Year's Eve...and if you are planning to be one of them, you should get there as early as you can. The MK often reaches capacity and closes for a while on New Years Eve. Be prepared to encounter enormous groups of people and not get on many attractions. If you don't have ADRs you will likely have to wait hours to get something to eat, even at a counter service restaurant.
Bob