I made a thing.

In all seriousness, I theorize it’s highly possible that Celestia and Luna decide to retire before this big fiasco with King Sombra, or after (I think more likely before), if King Sombra is part of a real return.

Other very strong possibilities (I think it’d be a bit off to just have him resurrect and appear out of thin air):

• It’s just a dream / nightmare sequence

• Time warp or interdimensional mishap

.

The Sparkle Harmony Tree looks like it imbued the Student 6 with the Elements, either as a safeguard against what King Sombra is doing (and the Mane 6 fail) or as an emergency for them to save the Mane 6 in the major problem.

The only thing that throws me off about the new trailer is where it looks like there’s a different castle where Starswirl pulls out 6 objects with his magic (the Pillars’ Elements?) and we know Twilight is carrying a bag of something.