-- Black Ops 2 is a direct sequel. While not set a few years later (the story is taking place in 2025 as compared to the first game's 1960s Cold War setting), the game will still be in the universe that was established by Black Ops 1 and a few characters from that game will reappear in Black Ops 2, with Treyarch promising that the characters will have changed.
-- Rual Mendez, the main antagonist of Black Ops 2, will have his story revealed. Players are promised to some actual backstory as to why Mendez wants to screw over the US instead of him just being a terrorist and/or a type of person the US doesn't like.
-- The game isn't solely set in the future of 2025. A few scenarios will send the player back to the 1980s, when the Cold War was starting to end. I assume this is where the horses will come into play, which makes me slightly sad that I (probably) won't see a bionic tiger fight a horse equipped with a laser rifle.
-- David Goyer, the man behind the story of both Batman Begins and The Dark Knight, will be writing/has written Black Ops 2's story. While impressive-sounding at first, David Goyer has also written some films that range from mildly entertaining to mediocre. However, most of Goyer's recent track record says more positive statements about him than negative ones, so this could go either way.
-- Treyarch wants your performance to mean something to the story. Studio head Mark Lamia stated that specific characters will die or live depending on your performance and choices in a level. Future story events will also follow this route of being avoidable and obtainable depending on player action. While I do doubt we will see Deus-Ex-like levels of choice, if Treyarch can keep the promise then the game will contain a single player campaign worth revisiting.
-- Specific missions will allow the player to do what they want to achieve their goal. Dubbed "Strike Force Operations", these missions are basically open maps that allow the player to find any solution they can to the problem they encounter. If the player wants to tactically command a squad of robots to achieve their goal then that choice is allowed, but picking up whatever armaments are available and taking the challenge head-on is also a valid option.
-- E-sport potential is a huge focus in the multiplayer. While not revealing anything about the multiplayer, design director David Vonderhaar stated that Treyarch wants the game move the game into a direction where it is extremely competitive and is like an e-sport. While I'm not a huge fan of so-called "E-Sports Titles", this statement does make me wonder what will happen to the quasi-RPG elements that have been the series mainstays since Modern Warfare 1, as rewarding players with physical enhancements slightly goes against the idea of everyone still having a chance of winning against everyone else.
After looking over those points again, I'm really interested in Black Ops 2. Even though it is yet another Call Of Duty game, Treyarch is molding the game series into a different (yet similar) creature that may keep the Call Of Duty brand fresh for another few years.