That's an interesting thought. I hope they make a bb2 but From/Miyazaki seems to have moved on from those games. The reason I ask is because it feels like a huge opportunity for Sony to capitalize on. The "Souls" name is absolutely huge in the industry and having an exclusive franchise tied to that could work as a system seller for sure.
I'm pretty sure they would risk souring their relationship with From if they start making their own "Souls" franchise. Like a port/remake of a game that already exists is one thing, but actually making that into a full series might be a pretty serious risk of causing problems with From.