Internal presentation dated September 19, 2017 pitching the idea of a G4 finale movie to fill the gap between G4’s 2017 movie and G5’s then-planned-for-2020 movie.
Hasbro always intended to have another MLP movie, internally known as “MLP Movie 2”, to follow up the 2017 one but their plans for what this movie would be went through many changes. It was first going to be a FiM series finale, then it became the G5 premiere movie for the original “G4 reboot” version of G5, before eventually turning into the G5 premiere movie for the “G4 sequel” version of G5.
At some point between all that, after committing to “MLP Movie 2” being G5’s movie, Hasbro briefly considered returning to the “FiM finale” movie idea anyway as a third movie to fill the gap between the 2017 movie and G5’s movie.