Considering how much time it took James Cameron to get his script right, it was possible that things had changed over the last seven years.
Way back at the beginning of this decade, when we thought Avatar 2 was coming sooner rather than later, James Cameron said that that Avatar 2 would take place primarily within the oceans of Pandora.
While we’ve heard essentially nothing about the plot of the next film since then, the fact that the reef people will be part of the story would seem to indicate that there’s a good chance that plot is still intact.