IF they do use a FP booking system - they should do the similar technique to what they do at DLR. You make FPs available on a first-come first-serve basis in the morning. NO pre-booking of FP for the show. There is no 100% "fair" way do it (you would still be "punished" if you come to the park late), but I think this is the most equitable way. Otherwise, the show will always book up at close to 60 days out.
I am hoping that there will also be dining packages available that include reserved seating. We did that for Fantasmic at
Disneyland in August. That way we were able to insure good seats ahead of time without being at the park early to grab a FP. We did the package on our arrival day and didn't get into the park until afternoon. We had a great meal and great seating for the show.