I want more occults. I want improvements to current occults. However, only the former is the most reliable (standard transaction: money for new pack with new content). The later, however, as much as I would love an update, I cannot think of a major update or rework to a DLC pack. Just base game (which means plant sims have a shot). The things that get updated are added to the base game, like photography skill.
So unless Aliens or mermaids are going to be made base game (I think this could be more easily done with Aliens because there is still a lot GTW has and some Alien stuff can still be exclusive to that pack like the scientist interactions), I do not think we can avoid DLC for DLC to get more content for them. If I like that content, I do not mind paying for it.