It has been confirmed by one of the directors that in season 3, Rikki and Zane break up and Zane starts dating Sophie, Will's sister. Using this to her advantage, Sophie tries to get the cafe renamed "Zane's" instead of "Rikki's". The couple will be a rerun of the relationship between Lewis and Charlotte.
There has also been speculation that Sophie finds out about the mermaid secret.
(This is mostly during episode 20, "Queen for a Day")