Good points. 6,000 might actually be max heading to the resorts on a very crowded day. There are about 7,400 rooms serviced by the gondola line so even at extreme high occupancy times there are probably roughly 7,000 rooms occupied. Each room probably has 2 to 3 guests on average so let’s be conservative and say 3, that’s 21,000 guests but they are spread between all 4 parks, Disney Springs, hanging at the resort and trips off property. 6,000 would assume almost 30% chose EPCOT that day and that they all stayed for Illuminations and all tried to leave right after the show. On most nights the number will be much less than that. The one wildcard is factoring in how many guests are boarding to hop over to DHS for a later evening. When SW:GE first opens that number may be higher. Remember how they kept Pandora open late that first summer and it stayed relatively busy.
For perspective the monorail system as a whole moves 150,000 daily riders on average per day.