I think it was around a month or so ago, Fujino mentioned that he couldn't make super long H-scenes because he needed to be mindful of the space it took in the game, since RPGmaker has a limit on how big a game can be.
At the same time, he mentioned we were more or less around the 50%~60% mark of the game, taking into consideration how big part 2 is already, there is no way Fujino will be able to fit everything he wants for the game without surpassing the memory limit of the game.
That's why everyone is so sure part 3 will be a thing.
Now, that being said, nobody truly knows when part 2 might finish, since Fujino has said nothing about it. (He himself probably doesn't know.)
I would say, judging by what makes sense from the point of view of the narrative, I can’t see it ending in less than 5 updates.