At some point in the series, mermaids will be revealed to the world.The mermaids are being harmed a lot by human activity and they have no real power to stop it. They can attack a few ships but ultimately, they're outnumbered. While revealing themselves will open them up to persecution, it will also give them the opportunity to advocate for themselves, and to work with humans for the betterment of both species. This will be done at least before the last season so the show would have several episodes to address the challenges and aftermath.
Ryn will try to make peaceful contact with other mermaid packs.It has been established that other mermaid packs exist, though are territorial. The show may be setting up for other mermaid groups to appear. Ryn, with what she has been learning from human society, will decide to try cooperating with other mermaids to deal with threats that they all face.
- Confirmed. Ryn travels to Alaska to convince Robb's tribe to help her in her fight against Tia.
Other mermaid groups will have physical and cultural differences from the ones we've seen so far.
- Confirmed. Tia's tribe has different fins and coloring from Ryn's. Although it seems that mermaids are capable of changing those traits at will, so perhaps those physical differences are a way for mermaids to indicate which tribe they're part of. Robb's tribe are all born female, but can change sex in order to reproduce. They all have light blue eyes.
Robb is going to have good intentions towards the mermaids but will end up wanting to do something that could hurt them.
- Given that Robb is revealed to be a merman, this is likely jossed.