The optimistic interpretation: Black Ops 2's theme of high technology turned against its owners by a hack-happy enemy will lead to a Terminator 3-style situation whereby tech just cannot be trusted. Even the noble toaster will be looked upon with suspicion, before being promptly shot in half. Can you imagine that? A world without toast. These terrorists are monsters.
Anyway, modern technology as much a risk as an asset, we'll eventually be forced to eschew as much of its use as possible, leading to a cool and clever set-up during the second half of the campaign in which we 'go analogue', combating our own advanced hardware with more antiquated, more traditional tools of warfare.
Enter the horses vs. choppers encounter seen in the trailer, in which we must use the versatility of our swift but vulnerable steeds to evade an ever-present metallic threat from the sky, using environmental and manoeuvrability advantages to gain the upper hand. Horses can't be hacked, you see. Unless you have a really nice carrot, or an absolute crapload of sugar lumps.
The pessimistic interpretation: The horse bit will be one of the campaign’s ‘80s-set levels, and will be just another Call of Duty on-rails shooting bit, only with the skidoos reskinned with horses. Horses are cool since Red Dead Redemption, you see. Just ask Uncharted 3.