Persona 5: The Royal, is indeed the Golden; enhancing and adding in new content, but after the Okumura case, Kasumi becomes the 8th member of the Phantom Thieves. And in the process, it's her instead of Akechi for the immediate for Sae's palace. And as the game continues, Yab uses Kasumi as a form of..third-man, as she inconveniantly steals the dreams and desires of the various Phantom Thieves. And the finale is set where Joker saves the members, and sees all the various dreams/desires that they hold; while stopping Yab and saving Kasumi.
And after the Sae Palace, Akechi becomes involved; determined by the choices you make with you and your confidants, and could result in a good or bad ending.
A guess, but it could make a lot of sense given the context of the trailer.