I was just thinking... have they announced which controller scheme they've chosen to go with in Halo 4? Halo Reach's or Halo 3's? I really liked Reach's for the melee combat, but 3's action button (RB) felt a lot more accurate in it's place.
Really, in this regard, it's a just a matter of finding whether the action button or melee button with be on RB, X, or B.