Plus, his previous game "Lewdest Labyrinth", had about 4-5 areas (I don't remember how many exactly, it's been a while), and this game's v2 demo already has 3 areas in it, so unless the dev wants to make Night Labyrinths noticeably bigger than "Lewdest", then I'd hazard a guess that we have already seen at least half of the planned content area-wise, maybe more.
And the dev also said after he released the v1 demo, that he originally planned the next release to be the full one, but because development noticeably slowed down, he decided to release the v2 demo.