Huh? I mean, sure, they could add content to the game till the sun goes out, but at some point a game is just considered feature complete by its devs for one reason or another, whether just due to them simply wanting to move on, or having managed to achieve their goal with the project. I can't really speak for Remtairy obviously, but considering things they've said in the past, and in general how long the game took to make to begin with since its a small development team behind it, I doubt you'll see much more beyond the Gym DLC, though I also haven't really kept up with the games development post release.
Really, I'd say just be happy with the fact that you got a game this unique in a pretty repetitive and uninspired space of gaming, and one that in general actually has a pretty complete feeling cycle of gameplay from start to finish. Plus, it even has mods, which isn't the most common things for hentai games even these days, so if people really want more content for it in one way or another, its always something you yourself or mod creators in general can think on to add the sort of content that you'd wish for. I'd kill for an official pregnancy option to the game, but I also understand its really just not the creators preference for this project, so in the end it is what it is. ¯\_(ツ)_/¯