For now they will just be focusing on a group of species that are being more developed. Especially being the second game, that is going to happen. Guessing a plot for a third is going to be majorly way OUT there from where we are now, which is kinda funny how things are going to be different once a third comes.
@The Rabbit Twitches The way you suggested the Salmon Run plot reminds me of Beyond Good & Evil. Even if the gameplay of itself is going to be like a zombie run till you could no longer fight, but it as least something to consider in the near future within the next game.