Wouldn't that be the Whispers and aren't those independent?

Honestly, with a different timeline, Genesis might appear to beat the sh*t out of Sefiros and I would 100% approve of that. Might include Angeal or not, depending on how far Square intends to revive people. Or alternatively, Elfe will appear. She's the only one that has in fact match Sefiros's power and fought him face to face, though Weiss falls to a similar place (hence why he became a superboss in InterMission), but has never fought Sefiros (and unless he does kill him, I don't need that fight to happen).

I don’t think it’s the whispers.

The wispers are trying to counter the changes future sephiroth makes in the destiny of the party and the world. So i think future sephiroth will bring new threats to the story.