There's a ton of stuff coming out of BlizzCon. New Campaign details out of HotS, and they announced the new Multiplayer units! They're introducing Battle Hellions, hellions that pretty much transform into Firebats and back, turning from fast light vehicles into tough as nails close range fighters, Warhounds, faster, lighter, cheaper Thor-like units that are designed to break siege lines out in the open, and Shredders, that emit a big AOE damage area that turns off if there's any friendly units in its field. Area Denial weapons that have to work by themselves to work. Also, Thors are getting relegated as an End-Game unit, where you can only have one, but they can now be more powerful. Really, I'm ecstatic about the Battle Hellions.
Zerg is getting Ultralisks that have a burrow charge, so they don't get stuck behind zerglings and get stuck in right away. Vipers are flying casters that can do some sick things, like pull units over and a swarm cloud that blocks line of sight, I think. It also replaces the Overseer. There's also now Swarm Hosts. They burrow, then create little locusts that will attack in the direction you set the rally to. So now Zerg has a great siege unit.
Protoss is losing the Carrier...and getting the Tempest. Has AoE Air-to-Air that does crazy splash. Your Protoss buddy that hates Mutas, probably has to change his pants now. But it's going to require a fleet beacon, so it's meant for killing that Late game muta flock. There's Replicants, that can copy any non-massive unit it sees, but it's 200/200, and Oracles that harass, but deals zero damage. Instead, it can phase out buildings, and Entomb minerals, requiring the opponent to attack the "bubbles" or wait it out in order to harvest minerals again.
Also, the existing units will be getting changes. Reapers won't have the Explosive charges, but can regen out of battle. BC's will get a speed boost CD. Hive tech can research Burrow Move for Banelings, Corrupters gain Syphon, which does DoS to a building and harvests resources, and there's a speed upgrade for Hydras off creep, so they'll be really good late game. Protoss will lose the Mothership and Carrier, but the Nexas gains Recall, and the ability to turn buildings into proton cannons for a bit, to prevent cheese, though it may cause some cheese.
Of course, none of this is final, but it's going to be awesome if these units make it in one way or the other.