It’s fairly common for next episode previews to end with some sort of catch phrase in anime.
Digimon: Next time, see how the adventure evolves!
One Piece: I’m gonna be king of the pirates!
Black Butler: I’m simply one Hell of a butler...
Evangelion: And of course, there will be more fanservice.
It’s just a little bit more flavorful than “see you next time!” Which some anime do as well.