If the park reaches a certain capacity even those who are guests at WDW hotels will NOT be allowed into a park, even with a PS! This has happened on NYE and Christmas Day for us in 1999, 2003, 2004 although it was only MK that closed and it was by 11am. I have been there on Easter Sunday(it was a ZOO-even worse that the holidays), but I don't know if MK was at capacity. They will first close to nonWDW guests , then to ANYONE if the numbers are high enough.
Connears