There are going to be three main endings, each with three sub-variations, and a sorta-secret fourth "canon" ending, plus each of the girls will have a unique ending based on whether or not you maxed out their love stat and certain decisions you make regarding them in Act Three.
There are no "good" or "bad" endings - the game doesn't make any judgement calls on you, so the ending you get will be based entirely on the decisions you make, and whether you think it's "good" or not will be entirely up to you
(But really, don't worry too much about it. I'm not interested in creating endings that punish players for participating in the game mechanics. There won't be any "you suck and now everyone is dead or sad" endings)
Almost... I'm only one person so I can't go as in-depth with the system as the Summertime Saga team can, so no "gradually changing body" graphics, for example. Sorry!
The current idea is that you will attempt to impregnate the girl, and if it works then after a few days she will appear with a pregnant belly and inform you of the fact. At this point you won't be able to do her normal "Let's be Naughty" scenes, but you
will get unique pregnant-only sex scenes instead. After a little while the girl will give birth and then you can repeat the cycle if you wish.
Yup! She's actually going to play a pretty integral role in Morgana's story so I'm not going to reveal anything about her, but she'll definitely be back.