|What would have been: This song was written to replace "God Help the Outcasts." It was thought that God Help the Outcasts was too simple and humble for this moment; Esmeralda needed a song that would make a grand and powerful statement. Thus they wrote Someday, to give Esmeralda a mighty anthem rather than a humble prayer. But eventually it was discovered that at this point in the movie Esmeralda wasn't in the status to sing a triumphant anthem, but rather this was a humbling moment for her. So they returned to the original song, and Someday ended up in the closing credits.
What I think: I think it might have been interesting to have an anthem in that scene, but I'm in agreement with the directors that it was a humbling moment for Esmeralda and her singing all trimphantly would have been a bit out of place in the context. But I hear in the German musical version Esmeralda and Phoebus sing Someday in the dungeon....maybe that would've worked, I dunno. Anyway, I like it in the credits.