Wait... Covenant Carbine is back, for sure? I cannot wait for Halo 4. SMG was amazingly fun, but it isn't a big deal if it doesn't appear in Halo 4. I am sure it will, though. Look, this is after Halo 3. Halo: Reach was before Halo: Combat Evolved. Halo 2 introduced the SMG, and throughout the STORY LINE, not the games, it has been there.
Example:
Halo 2 introduced the Covenant Carbine, and it showed in Halo 3, the game directly after Halo 2. It was gone during Halo: Reach, but it didn't show until AFTER Halo: Combat Evolved. So wouldn't it make sense for it to NOT be in Halo: Reach? Exact same thing with the SMG. The SMG was the primary weapon in Halo 2, leaving out the Assault Rifle. I am sure out 1/6 of the games where the primary weapon was the SMG, it would make a return.