Blizzard Entertainment released teaser footage from the Zerg-themed expansion at its annual convention, but is yet to reveal a release date for the title.
Heart of the Swarm is the second of three StarCraft II instalments, following on from last year's Wings of Liberty. The studio confirmed that it will enter beta testing within the coming months.
"We're coming up to it pretty quickly. I don't have a specific date, but certainly months - not years or anything like that," said lead producer Chris Sigaty of the beta timeframe.
View the BlizzCon 2011 preview trailer for Heart of the Swarm below:
Blizzard has also confirmed that the expansion will feature a host of new units and additional gameplay mechanics. Players will have the option to choose between sub-species of Zerg units and customise their powers through the swarm adaptation feature.
StarCraft II: Heart of the Swarm is expected to be released in 2012.
> Read our interview with StarCraft II senior designer Jonny Ebbert