This is making me think of
Disneyland when they have the early entry for the hotel guests but the rest of the guests are held at the entrances to all the lands and the rope drop happens there. I think there are some good and bad about this:
Good
-no more arriving before rope drop but getting stuck behind the people who don't know how to use the finger prints at the entry and slow down the lines
-for those who like the early morning Starbucks this will be nice, I'm sure that will be open
-it will be nice to have some time to mill around on Main Street and not feel like you need to rush to the headliner attractions
Bad
-no more train welcome show. who knows what the new welcome show will be. could be some very low key cheap show, or could be nice. Hard to judge now.
-this is something very small, but I took the Keys to the Kingdom tour before and it was really fun being on main street and viewing the welcome show from behind. As soon as it was over, all the characters practically race down the stairs of the train station and sprint for the backstage so that they get backstage before the guests enter.
I'm really not too concerned about the pre park opening main street pictures. I've had a few pre park opening breakfasts and I could never get pictures of the castle that were clear of other people, all the other breakfast guests are also milling around in front of the castle getting pictures. I've found it is easier to get pictures with no other guests in them in front of the castle at nighttime anyway at park closing.
Honestly, if you want the empty park pictures I'd book that early morning paid for hour. Probably costs less than a family breakfast at Crystal Palace.