I appreciate how you laid this out. I would most likely fall into category one and I don't see a huge need for the chatbots for myself, although I can imagine I might like an Alan-Watts-level companion more than many human friends.
I think I also worry the most about two, almost asking their human friends, "Why can't you be more like Her (or Alan Watts)?" And then retreating into the "you never tell me I'm wrong" chatbot, preferring the "peace" of the chatbot over the "drama" of interacting with humans. I see a huge "I just want peace" movement that seems to run away from the messiness of human interactions and seek solace in things that seem less messy, like drugs, video games, and other attachments/bonds, and chatbots could probably perform that replacement role quite well, and yet deepen loneliness.
As for three, I agree it may help as a short-term solution, and wonder what the long-term effects might be. I had a great aunt in a home for dementia, and wonder what effect it would have if someone with dementia speaks to a chatbot that hallucinates and makes up emotions.