There are overall tons of points which makes me think that the entire story of One Piece is going to roughly play out as the Skypiea Arc did.

– There are the Ancient Kingdoms forces (Shandians)

– There is Im = God Enel

– There are people (Skypieans) who are “good” but are actually controlled/brainwashed by God (Celestial Dragons/God Enel)

– There is the Ark Maxim of Enel (which is similar to Ark Noah)

– There is a promise from 400 years back that gets fulfilled (similar to JoyBoy’s promise from 900 years back?)

– Forgotten history, Void Century = forgetting that they were part of Jaya

– Lost Kingdom, Ancient Kingdom = Sky Island’s Upper Yard

– Impact dials are described as being forces that impacts the person “from the inside” exactly like the Advanced Armament Haki.

– There is a final survival match-up that happens in a cage similar to Dressrosa arc.

– There are paintings of ancient warrior fighting a multi-headed hydra, like Orochi in the ruins of Shandora.

– The “old” God is one of the fighting forces involved in the final battle (this is equivalent to the original rulers of the Ancient Kingdom)

– The promise was between the Shandora’s head, the warrior Kalgara, and Noland, i.e. two kings.

– Luffy satisfies the promise which is heard by the descendants of the Ancient Kingdom and Noland.

So overall, I think the way the final fight plays out in Skypiea is roughly how the final fight is going to play out between Luffy and Im.

*Theory by __tremb__