The dev has said the Main storyline could probably be completed with a couple of updates dedicated to that. But there's a number of other things he wants to implement as well. And I bet he wants to find ways to weave at least some of the Side storylines into the Main, which would be easier if those were at a point he can work with over retconning/redoing stuff to fit those Side storylines in afterwards.
The next update is due later this month. With it the last existing girl will have her storyline brought to where she can give birth and has a reasonable "stopping point." There are still a few more girls he wants to add: upgrade Daiyu to the harem, add Dwarf Girl, add Cath, strong possible for Orc Girl, and strong possible of a couple more anthro "pets" for the dungeon. (I'm starting to question whether Qetesh and whatever hatches from ED's egg will actually be added to his harem, though.)
I'm betting at least four updates after this one, more probably six to eight to get everything tidied up. There's very roughly four updates/year, so one to two years. Maybe.
The dev is creating PQ by himself. Story & dialogue, images, coding, all of it. He has a QC person to check things before test builds go out to high-tier supporters, and pays for assistance creating animations, but that's it. He also has a full-time job, and a family with kids.
