The third Goddess (Farore) was represented as the Oracle of Secrets, she lives in the Mako Tree in both games. There is no finished third game, Nintendo wouldn't have done something stupid like not releasing one of (if not the) strongest franchises worldwide. If there was a third game, it probably never made it beyond early production before they realized it was not worth it. End of story.
So I remember in the trailer that Naija has the ability to "jump" out of the water, like a dolphin. Given that...is is possible to, say, leap onto some dry land? My point is, will there ever be a part of the game where Naija is required to leave the water? Or would she flop around like a fish if that happened?