I was wondering whatever happened to episode Luna. There's apparently gonna be an episode Noctis too. It would be hilarious if episode Noctis involves playing as Versus XIII Noct.
Episode Ardyn, Peisode Luna, Episode Noctis and supposedly some kind of Finale expansion. I hope they don't change the ending but instead expand upon the world of ruin segment.
On ending changes, I do like Episode Ignis bonus ending. It's a pretty nice treat for players who actually put in effort for the final encounter even if it is non-canon.
My take is that the "alternate ending" in Episode Ignis is not really an alternate ending but a fantasy of Ignis has right after he tears up with Noct's farewell, a Lalaland type of ending deal.