It wouldn't be released WITH the map-pack because it's theoretically impossible, every map has all of the armor permutations built in. Releasing new armor with the maps would mean that those are the only maps that can use the armor. There are three possible explanations for this armor.
1. Disk Locked Content- Armor on the disk that requires a certain encrypted code that only the developers can unlock. Thus preventing teenage bedroom hackers from unlocking the armor.
2. Title Update- When the map pack releases, Halo Reach will need to be updated in order to accept the changes that the maps bring. In theory the game could be updated to either A: Unlock Disk Locked content, or B: Update every existing file to introduce new permutations that 343 and Certain Affinity created themselves.
3. Dev Armor- It could be that Certain Affinity and 343 made the armor for themselves on closed network tests just to give them the ability to practice armor building techniques needed for producing new halo games, or just because they can.
And let me remind you, Bungie said there would be no armor released with the maps, but Bungie is not in charge or even part of the map pack's production, so they wouldn't know what could or couldn't be added.