They wouldn't. There's no need to.
14 isn't a failure of a game in its current state, and they're already doing a stat squish with Endwalker. So there's no reason to reset anything.
Eorzean maps have just been redone six months ago so there's no justification for scrapping them.

So any 'Calamity' will be done entirely for plot reasons, with no hard consequences for gameplay.