I'm expecting every single one of the flashback scenarios—Nibelheim, Corel, even checking the PC in Gast's place—to be fully playable sections. I think SE wants to do a 7-part remake, but I highly doubt that will come to fruition. We should almost certainly expect brand new sections and maybe even some of the unfinished / cut content to be completed if enough of the original team members are like "oh, hey, remember that idea we had".