Even if Catalog hadn't confirmed that the ODST divisions remain in the Marine Corps to the extent that confirmed their role within the service there's still vague indication that would let you know they're still kicking. The MJOLNIR Helljumper armor set in Halo 4 is an entirely different model to the one we saw prominently in Halo 3: ODST. I doubt Materials Group would bother upgrading this series just for the more nostalgic Spartans if the ODSTs as a whole were disbanded. The eggheads would have probably told all those bucketheads to stop being nerds and get some Air Assault or Soldier armor.