fanofpooh, I have been to NYE at Epcot 3 times and the MK once. Every time I entered the park of my choice in the early AM and left it for the majority of the afternoon. We have APs, but we still get our hand stamped on that day. We have never had a problem returning to the same park in the early evening. Park hopping may be different.
This was posted on rec.arts.disney.parks newsgroup a many years ago by a CM. I'm not sure if it is still valid ... maybe a current park CM will know.
> On Tue, 01 Dec 1998, Drake Whimsy
> (Robyn Johnston) posted
>Seven Levels:
>The official line (as the MK gate computer sees it) is:
>Defcon 0: normal operations
>Defcon 1: (not used)
>Defcon 2: parking lot closes
>Defcon 3: ticket sales alerted not to sell for today's entry
>Defcon 4: park hoppers re-entering at MK & resort guests only
>Defcon 5: re-entering MK guests & resort guests only
>Defcon 6: re-entering MK guests only
>Defcon 7: closed
As you can see, re-entering park guests may still be allowed in when park hopping guests are not.
Why don't you have a back-up plan? Try to hop to the MK (have your PS# in hand! That'll help.) and if you are denied entry then hop on the monorail and spend the night in Epcot. Personally, I think you're going to be OK. When we returned to the MK last year no one was denied entrance.
BTW, are you staying onsite? Parking is the real problem that whole week. The MK parking closes before noon almost every day.