Contemplated making a post about this, as I play PSO2 quite a bit... but if this does happen in the future, I expect PSO2 to get costumes(probably the starting costume for miqote and possibly the warrior set, as they seem to like showing the main character in the trailers using that quite a bit). If they make this a little more elaborate like the Border Break collab, then we might even see a FF boss as part of a city event quest or something, perhaps maybe Garuda or the end boss of the main story since she imitates a lot of the bird darkers from the game, and the end boss is well... I don't need to say more. As for FF? We'll probably see a HUmar and HUnewearl outfit, and at most, we may see a small event with a fate where you fight Falz Hunar(but I sincerely doubt that'll happen).