Hmm. Isn't Darksouls and bloodborne semi open world anyway...yeah. Hell the Dark souls is more open than some semi open like DA: Inquisition. A souls-borne open world would remove the metroid vania level design which is pretty much the core aspect of what makes souls games fun.
Yeah, I don't want Soulsborne games to be any more open than the first Dark Souls. Basically corridors/rooms/arenas, but with intertwining paths and shortcuts. I like that the designers control how and when you face obstacles for the most part. That gets lost when you go open world.