I think Zanith is going to add two more girls, one is going to shack up in the room intended for Blair, and the other is going to unlock the room beside the first floor bathroom.
My point in arguing that it is not the right time to add another housemate rests upon the fact that if too many girls are added in a short amount of time, it slows down the amount of content we get with the girls overall with each update. Just because we have many girls it does not mean that the game or update itself is good.
Biggest example of this in the moment is Mythic Manor, sure there are many girls to choose from in the game, but the amount of content added to each of them in the updates is laughable, to the point that it feels like we waited for 6 months for 10 minutes of content that added nothing to their story. This is a big reason why people are turning away from it.
I like how Zanith approaches their development. We get consistent updates every 1-2 months and every update focus and progresses the story of one of the girls, while adding one side event or repeatable scene. They do not feel pointless and are not a waste of time.