In XY Geosenge Town's houses get knocked over by the Ultimate Weapon.
Like this :
Will the Ultimate Weapon disappear or is Geosenge forever ruined in the game ?
The Ultimate Weapon disappears after you defeat Diantha, and after the postgame narrative where Floette-Eternal returns to AZ. However, there is an enourmous crater in the middle of Geosenge Town, and there are still upturned buildings and rubble. That does not go away.
It may revert back to its normal state but most likely to stay the same. Even though in future games (If there is one) it might return back.