A Blizzard fan's dream come true is the previously announced Blizzard DOTA. BlizzCon 2011 opening ceremony showed a preview trailer of the custom map and it included heroes like Arthas, the Queen of Blades, Zeratul, Witch Doctor and other units from the Blizzard Entertainment franchises.
Blizzard's custom map DOTA was mentioned to be released at the same time as Heart of the Swarm. In the video below it is said that it's "coming soonish™".