I agree with you. Carl is pretty much toast at this point. Though some people are still hoping that the long suggested threesome between him, Anna and Rebecca can still take place in some way. I believe that it won't. It was always going to be difficult to stage, without running afoul of patreon's rules regarding incest. The Devs are not going to make a patch to get around it, which pretty much means they can't depict any full-on sex between Anna and Rebecca, however much they'd like to. So anyone expecting this to happen during the upcoming porn scene involving Anna and Rebecca, should think again. Yeah, it will probably get steamy between the two of them, as it has in the past, but they're not going to have sex with each other. That will happen with the other two guys in the scene.
By making Carl into the game's true villain, they can pretty much sidestep the need for that threesome to ever happen. As well as freeing up time to pursue other content, by creating a pretext to get rid of one of the game's main characters.