I just Love Love Love Supernaturals so I hope they make something like it for Sims 4 soon, I hate to wait like for Sims 3 with all the "boring/ normal" (to me at least ;) ) expansion packs. I have them all though (but got the normal ones much later -and like them for different things (except pets, don't really like it at all). But Supernatural is my favorit because of the simple reason that you can play with different species not just sims, it makes what would be normal gameplay, like having kids etc, much more fun to me as you can mix and match. I would especially love if they could actually make it so there is hybrids this time, like meant to be ones, that would be so cool! I do get that that would require more work and coding tho :/ I've been thinking a lot about this recently and instead of getting stuff that we already got and can play with in Sims 3 I would think supernaturals like angels or demons would be awesome! It would be so much fun exploring new supernaturals :D
Edit to add: And getting new supernaturals would also make people more interested in buying so they can try them out I think. If someone has already decided they don't like -say werewolf in Sims 3, they probably won't get a pack for the Sims 4 with the same thing in it.