I've been wondering about that too. From the trailer, as far as things like armor/weapon/architect design we can look at a few different things: marines armour and weapons, Chief's armour, warthog, and the beam emitters.
In my opinion this is what each looks like to me:
Marine armour: hybrid
Marine weapon: modern
Chief: hybrid, heavier on the classic side
Beam emitter: modern
Based on what we've seen so far I think it's looking to be a good mix.