http://forums.ubi.com/showthread.php...IGE-FAQ-Thread Check out that IGE - In Game Editor, thread which has some questions and answers listed, water at different levels they said they are looking into this and waterfalls,
Destructibility - I would hope we get some items that degrade, blow up - but I am not expecting to much - choosing weapons in the editor is a question we have not yet got an answer to.
DLC they have not yet discussed but there are a lot of different bonus packs that can be purchased, My thoughts of DLC is extra game modes, new editor items, multiplayer maps and single player missions but maybe 6 months after the games release at the earliest.