So far, Infinite has no way for multiplayer versus AI. And I usually think that is one of the best things for Halo, having a team of diverse experiences battle on a mode. Especially since everything is lore now, it gives a reason for it to exist.
When it comes back, I hope it is about the multiplayer Spartans find out about Chief and Infinity and is sent to do firefights battling Banished across the ring. (If you play the tutorial, multiplayer has nothing to do with the campaign, nor has any idea what is happening).