One of my coordinators said to me that if the guest can actually GET to the gate during a phase 4 closing, they would let them in. That is a pretty big challenge since all forms of transit are stopped from entering!
Just for the record, phases are (they added a new one!)
Alternative parking: Due to limited parking, guests arriving at MK should use alternate parking at Epcot and use Resort transportation to return to MK.
Phase 1: Guests with MYW base tickets, one day tickets, guests with no admission, and CMs using a main gate are turned around at the Auto Plaza.
Phase 2: Only resort guests, AP/PAP, Park Hoppers, guests re-entering the same park admitted, ONLY if using a taxi or resort transportation. (Auto Plaza is closed)
Phase 3: Only resort guests and AP/PAP admitted. (Only resort transportation)
Phase 4: Closed to all guests. (basically no incoming transportation)