Posted here are upcoming features in the game that have been teased or found in the code, but not released. If information posted here is outdated and has been added, feel free to delete it.
Here is where a lot of the discussion on upcoming feature are being held: https://wanderers.userecho.com/
Deer EditRezoner has talked about adding deer for a while now, but currently he is debating whether he wants to add them or not. There are numerous sprites of deer in the games code, but no code for them.
Storm clouds (proposed and planned on forums) Edit
These storm clouds, proposed by Egzekutor, are supposed to be darker than normal clouds, and tribes underneath them will have a chance of having their minions struck by lightning, dealing damage and possibly lighting trees on fire.
Mages are soon to be added to the game according to Rezoner. Not much is known about them yet.