Star Craft 2 Heart of the Swarm

StarCraft II: Heart of the Swarm is an upcoming sequel and expansion pack to the military science-fiction real-time strategy game StarCraft II: Wings of Liberty and part two of the planned StarCraft II trilogy. Part three is titled Legacy of the Void.
The expansion will include additional units and multiplayer changes from Wings of Liberty, as well as a continuing campaign focusing on the Zerg species. It will span approximately 20 missions and will be priced as an expansion set.Currently no release date has been announced.
The game is expected to have around 20 missions, and will be a sequel to Wings of Liberty, taking place two years after the previous game, in 2506.The player will play from the perspective of Sarah Kerrigan, recently returned to her human state.At Blizzard's 2011 BlizzCon conference, it was revealed that Heart Of The Swarm will feature 7 new multiplayer units, while removing 3 and changing the abilities of existing units and buildings. The exact modifications may change as development progresses.
The changes announced at BlizzCon 2011 are as follows:
The Terran race will feature two new units: the Shredder, and the Warhound. The Shredder deals area damage but only when in a stationary mode and provided there are no friendly units present. The Warhound provides a fast anti-air unit that also does good damage to ground-based mechanical units. The Thor will be changed to an "ultimate" unit, akin to the Protoss Mothership, limiting the player to having only one at any time. Its functionality will be changed, and it will not be able to shoot air units. The Hellion will have a new battle mode added, which allows it to transform into a heavier and more powerful unit. In battle mode the Hellion will do increased damage but in an arc in front of it instead of in a line. The Ghost will have its "Cloak" ability changed to be a one-time cost for a time-based duration rather than a constant energy cost over time. Reactivating "Cloak" while calling down a nuke will not interrupt the nuke strike. The Battlecruiser gains a "Redline Reactor" upgrade which acts as a cooldown-based speed boost. Lastly, the Reaper has its special building attack replaced by a passive health regeneration ability when out of combat. 
The Protoss will gain three new units and lose two. The Replicant, the Oracle, and the Tempest will be added and the Mothership and Carrier will be removed. The Replicant is able to transform into any non-massive enemy unit and will have any upgrades that have been researched for that unit. The Oracle provides several abilities that are useful for economic harassment such as preventing mineral harvesting, granting vision of enemy buildings and stopping buildings from researching or producing. The Tempest is a capital ship designed for providing large amounts of air damage. The Mothership's "Mass Recall" ability has been moved to the Nexus which will also gain an "Arc Shield" ability giving it some limited emergency defences. 
The Zerg will receive two new units and lose one. The Overseer will be removed and the Viper and the Swarm Host will be added. The Viper has several abilities: "Blinding Cloud" restricts ground- and energy-based attacks, "Abduct" pulls a unit to the Viper's location and "Ocular Parasite" allows any friendly, non-massive unit to be turned into a detector. The Swarm Host spawns a constant stream of slow-moving melee units called Locusts when burrowed. The Corruptor's "Corruption" ability is replaced by "Siphon" which slowly drains health from buildings converting it into resources for the Zerg. Ultralisks gain a "Burrow Charge" ability allowing them to quickly reach battle sites. Banelings will gain "Tunnelling Claws" similar to the Roach. Lastly, the Hydralisk will have a researchable speed boost when travelling off-creep.