A few more quick Korra relevant speculations based on the Seven Havens trailer...
Korra clearly has grey hair. It's difficult to determine if this clip actually has flashback type accuracy (probably not imo), but at least it suggests that Korra wasn't extremely young when... whatever happened ~happened. It suggest Korra would be 50-70 years old imo.
Also just the fact that it's now confirmed there's been several generations of timeskip + context of how people like Janet Varney talk about this series, it makes me consider if not only did Korra not actually turn evil and destroy the world during this "apocalypse", she might also have not even died and lived somewhere in hiding for years after. Just a total loose shot here.
A few other clues about how Korra's world developed:
These are the images shown while the voice over says the modern haven city needs to be prepared because "long ago our ancestors weren't prepared, and the Avatar let us down". The cities that seem to be experiencing the cataclysmic event already seem to have haven-like structures / the other one seems to possibly be republic city (which tbh at this point, is like, a day in the life of RC).
This suggest that it wasn't just a sudden out of nowhere event, but that the world had been adapting to changes possibly for decades (which is already the case since lok book 2). This is interesting in terms of how much Korra and her friends could have left intentional legacy imprints on the world of Seven Haven and humanity's survival.
