No Guests and No Split Screen are mentioned separately so I assume this will be the first Halo playlist at Max Local Players: 1 (that's not Score Attack)
Unfortunate, but somewhat necessary, especially if they start putting Forge maps into rotation.
I'm really hopeful they learn their lessons with Reach and 4 and either make it max 2 per box, or just don't make a game that can't handle full splitscreen over the internet.