2. Other Na'vi Clans
These were hinted at in the first film leading up to the huge final conflict, but the only tribe of Na'vi that was focused on in any detail were the Omaticaya in Home Tree. The other tribes and clans that Jake recruits to fight the humans are barely seen and definitely not in any detail. I'd therefore like to see more of these and other clans in the sequels, even if only briefly to build the world out some more and give it a bit of depth. However, the way Cameron might go about revealing these other clans would also depend on the story itself, but their involvement could also be quite important depending on this story. Maybe Jake and Neytiri need to take some kind of big journey upon which they encounter other Na'vi clans? Maybe these clans live off the sea, opening up the opportunity for the underwater segments Cameron's already confirmed? Naturally I'm just speculating, but I think introducing other Na'vi clans could work well in the story's favour and could link well to other new elements that Cameron may bring to Pandora.