The story will focus on Kerrigan after Wings of Liberty as she gains more power and focuses on her revenge on the Dominion. The game will have some more RPG-elements with Kerrigan being a main unit in the singleplayer. Upgrades and the focus of how you evolve will be gained through missions since the zerg gain power by infesting planets and their inhabitents. I won't go on much more to avoid spoilers but I'll end by saying that the game takes 20 hours to finish.
I will go over each race going through removals, changes and the new units:
None, Blizzard says that Terran " is the most complete race", and seeing their results in Korea they might be right.
- Reaper: loses his d8 charge attack (the attack they use against armor and buildings) and it'll gain a (researchable?) HP-gain skill.
-Thor: is now a "hero unit", you can only have one. It's also very late game and will be bigger, slower but more dangerous.
-Ghost: their cloak abillity is now more of a spell. You cast it and you can't turn it off anymore. So it requires a set amount of energy now.
-Battlecruiser: will gain a new skill that temporarely increases their movement speed.
The Shredder : a factory unit that has two states. In his mobile state, it can't do anything. In it's stationary state it has an area of effect attack that attacks both air and ground. When there's a friendly unit nearby it stops the attack.
The Warhound: an anti-air unit that also has a good ground anti armor attack. But it has a short range on ground.
The Battle Hellion: a transformation for the hellion making it more robust but less agile.
The overseer is now gone since it wasn't very usefull.
- Hydralisks will get a speed buff that needs to be researched first.
- Corruptors gain a new skill instead of corruption that damages buildings.
- Ultralisks now have a burrow dive skill that allows them to quickly charge into battle
- Banelings now have the abillity to move while being burrowed.
The Viper: A flying support (detector) unit that has 3 spells:
The Swarm Host: A ground brood lord that allows for mid-game siege abillities. Good for attacking stationary defenses and map controll.
- Nexus now has two new spells:
The Tempest: A new capital ship that has an Area of effect anti air attack but also has a good ground attack.
The Oracle: A caster that's made from the Stargate and has a few harrasement spells:
The Replicant: can transform into a targeted enemy unit gaining it's stats and upgrades.
WARNING: These things can change.