I believe it's more likely they will release Halo 4 on the next Xbox console, not sure why, but my guess is they are severely limited in what upgrades they can make on the Halo game,
Bungie couldn't make a Halo 3 game with more content than it already has, ODST and Reach are evident of this.

I bet 343 Industries would be lazy like Bungie and use the Lockstep/synchronous model netcode for co-op modes. -_-

I really would like Halo 3 for PC, with a full EK and upgrades to the game engine in general to adjust console limits for the PC, and upgrade the distributed model netcode for full campaign support. /wishlist.