I was under the impression that Exposition was an "early access" to the game for people that paid for it. So they get into the game and get 3 months to set up towns and establish connections etc, before everyone gets in. So the changes to the landscape would stay from KoE, but not the people. So an adventurer could find a ruin from KoE while exploring, instead of everything being untamed wilderness.

If I recall correctly KOE is set to end around 50-60 in game years before expo starts,

while Expo is only supposed to be about in game 12 years before game launches.

In between when KOE ends and Expo starts the world will be left to the AI to do as it wills. Have wars, Have raids, Have natural disasters, ect

So things built in KOE may or may not still exist in expo. Families started or moved in KOE may or may not still be there when expo starts. Those families might have moved again due to famine or plague or lack of jobs. OR they may have been slaughtered by an invasion force.

So things built by players in KOE are not guaranteed to still exist come expo.

comparatively speaking, the things built with ep or in game during expo, will almost certainly still exist at launch.

While it is possible they will get destroyed during phase 3 of expo and some things probably will. But the majority will still exist come launch.

Comparatively speaking there is no guarantees at all what will happen to the player built things in between KOE and Expo. because as I understand it, the devs will just let the game run like a simulation at that point with the AI running everything for those 50-60 in game years. So no telling what might happen.

Even if you copied the save and had two independent copies running. They could end up wildly different during that simulation phase. Because this time the Ai decided to attack thru the pass, while this time they took the direct route and that led to a different outcomes of the war or whatever.