Now that 343i has released concept art for the upcoming Halo 4, I've got a theory on new armor that may be present in-game.
Artwork depicts forerunner combat skin. We could possibly see the addition of customizable combat skins to combat the "ancient evil" that we will be fighting! Most of the community has been asking for "MORE" customizable armor and this may be 343i's answer. Most of the artwork depicts Forerunner architecture, so I think it would be safe to assume there will be Forerunner technology present, including armor.
http://halo.wikia.com/wiki/Combat_skin
According to the wiki, the combat skins have class rating 1-18 (maybe higher), so this could possibly be an addition to the armory. I also think that the Spartan armor and elite armor will remain.
Keep in mind, this is JUST A THEORY!! All questions, comments, and critisizms are welcome! (NO name calling )