Though I love more women in the game, I hope that already existing characters will get their development (Jenny, Megan) too. And that not all new content is about the new characters.
I think Jenny is already at the end of her developement. There will be more content and actions for her as a Slave but I think developement/curruption wise that's the finishing line. She's already a sex slave, has no shame and is dressed in pretty much nothing. And Nicole is also one enslavement scene away from it.
Megan, Heather, Emily and Maria are also close to it (I think they have between one and two more "levels" before being enslaved), so if anything this is a good time to add new characters or add more stuff to ones who were less important (like the Aunt's family and the principal), as much as I want to see Emily's next tier of corruption already.
Biggest problem with the updates is that the dev has to do monthly updates because of the Patreon model. If he didn't do that and released an update every couple of months I think the updates themselves would be less disappoointing and frustrating (as they would have more content, and spread among more characters), but that's a problem for nearly every game that commits to monthly updates. The upside of having something new every month doesn't really balance the lack of substance of these updates to me.