There is a bit to fear cause mermaids suck, there isn't a reason to make one at all. You can't even dive around and explore the ocean.
I hope they can learn from the well put together Vampires gamepack they had come out a couple years ago. If they release their realm of magic with that much gameplay content, it should keep us busy for a long time.
I think mermaids probably just got tossed into their expansion because they wanted to charge expansion price for it.
It was a scam. We previously got a good deal with vampires and a new area for the price of a gamepack, yet they tossed in less content with useless mermaids and a buggy new area for expansion pack price. You can't even build underwater basements unless you use a mod. Building underwater basements would have been a great thing to have in the game.
