As for a small number of savvy guests...
High end for FP per hour at an attraction is 80% of capacity. (Ok it's 90-100 on some days but they try to stop at 80).
We all say Frozen Ever After only does like 1000 per hour so the math is simple - 800 FP per hour.
12 hour operational day and you've got 9,600... which is about 1/3 of the total park population of Epcot on a given day that has booked their FP for Frozen several months in advance.
And there's still a lot of people annoyed they can't get FP for Frozen. You really think they won't book the two Pandora rides and Rivers of Light ?