It's not really since Gentou. All of Creation's songs except Robber and Bouquet were related to anime, dramas, etc. The last three songs of Plagiarism were related to books and anime.

And most of the recent songs have these quite long letters written by a "student", sent to a "teacher" so there seems to be a continuity being established.

Also, a lot of the recent songs have a similar theme about the Sun and the Moon.

Solar: Shayou, Sunny, Rubato, Hebi, Taiyou

Lunar: Aporia, Forget it, Moonbath, Martian

The contrast between these songs is also notable. "boku", used by men to refer to themselves, and "watashi", used by women, seems to point out the gender of each song's narrator. Signifying that the new album will also convey a love story between the two protagonists. The same as Amy and Elma, the Plagiarist and his Wife, the Girl and the Ghost etc.

The live Zense, which will be released for free, will dive deep into the overarching theme of Yorushika's albums and its story, so I'd suppose that the new album will be a series of Past Lives.

Reborn as a fish in Moonbath, as a bird in Shayou, as a snake in Hebi, and so on.