I can't help but think that since the Far Zeniths are all dead that nemesis would no longer be a threat to Earth. There's no Far Zeniths to exact revenge on. Unless of course there were other Far Zeniths that stayed on the ship orbiting the Earth. Perhaps the members more responsible for the rage of Nemesis. There's always a chance that there's a third AI on Earth that Aloy doesn't know about yet. Maybe a failed experiment leading up to Cyan that has enough of a spark of life that can communicate with Nemesis as it gets closer to earth. Or, possibly Hephaestus now being exposed to Far Zeniths technology has gained sentience to a degree that it can control Nemesis and utilize the Far Zeniths collective consciousness to flip script on some of Gaia's sub routines. The ideas are endless actually.
