I would adore Bloodborne 2... but at the same time I don't think its necessary. I think part of the allure of Bloodborne is that while figuring out what's going on is pretty simple, figuring out why things are happening is impossible (I still think everything -- including killing the Moon Presence -- was so that the Moon Presence could breed.)
I also don't think a spiritual successor would work, since Bloodborne is so specific in its inspiration.
But that doesn't mean I wouldn't cream my pants if it were happening.