this game as potential, they need to add sex animation and add new character like a horse, zebra
This will likely never happen. It really comes down to how the game is made. Everything is composed of static images; renders from a 3d program. This means each potential scene needs to be rendered out as an individual image.
Additionally, with the vague nature of the player character, in that we don't know what kind of creature we are. Are we human? Somekind of furry? Then add onto the fact that I can be Male/Female and anything else, along with having breasts, not having breasts, having a dick, not having a dick, etc etc. So trying to account for all player choices in this scenario is a recipe for disaster.
Also trying to achieve this would result in an even larger filesize for the game. It's a common issue for Ren'py games. The games just get bigger and bigger to accommodate the massive amount of images for characters and backgrounds. It's also why you get other games like Testament of Minos being +20GB in size because the developer made everything 2d renders and has to render out every animation for their main character for every possible type of NPC they can interact with.