This is all conjecture, mind you.
Based on the First Look video, and what various game sites are reporting and so on, I’ve come to the conclusion that 343i are trying to build the matchmaking on a something for everyone concept. That is, trying to please the people who maybe don’t play a lot of Halo and prefer more “contemporary” series, along with the people who still love Halo 3.
343i seem to have access to Megalo (the brilliant software that allows Halo: Reach to implement new gametypes without a TU), so expect a similar set up in that regard.
Narrative?
It seems that the multiplayer will be “in-universe” to an extent. My money is that its UNSC Spartans versus Insurrectionist Spartans.
Progression System
Controversial, without a doubt. In addition to cosmetic unlocks, we’ll actually be able to get game-changing unlockables, although I’m willing to bet it’ll still blend with the traditional power weapon and map control gameplay.
We’ll probably be able to unlock some form of Perks, and possibly weapon upgrades or some kind of equipment. However, they’re stressing that it’s not a Call of Duty copy and paste, so expect differences.
I’ve also got a suspicion that you’ll unlock “fiction” regarding the Spartan-IV conflicts, like in Assassin’s Creed: Revelations.
Playlist Setup?
I’m guessing they’ll be going back to the Social/Ranked setup. Social is where we’ll see the primary implementation of the custom loadouts, while Ranked will most likely be more pre-determined, much like Halo 3. Again, this goes back to the “something for everyone idea.”
Good chance that they’ll also set aside playlists for gametypes like Infection, and eventually Grifball and Action Sack type gametypes.
So, does this seem reasonable?