This is just a wild, speculative, hunch I have based on an observation, so don’t take it too seriously. I don’t think our boys in black are coming back. I have a funny reason for this that actually makes sense when you think about it.
Let’s assume the Marine design in the Infinite trailer is the finale design that will be in the game. Well, from a game design perspective you usually try to differentiate NPCs with differing appearance (usually color). Up close the Marines are a washed-out green color, but from “personal space distance” they appear very dark, almost black. Now if you were going to put a black colored NPC (ODSTs) in your game would you really put another (different) black unit in? Not typically.
I know, I know, it sounds stupid. It does start to make sense when you really think about it though. Yes, I know it could not be the final design and they still could put ODSTs in anyway. Just food for thought that I wanted opinions on.