During Blizzard's annual showcase BlizzCon this weekend, the publisher announced a new Defence of the Ancients, based on Starcraft II: Wings of Liberty. A trailer was shown, showcasing the story where two Gods fight each other for fun.
You won't need a copy of Starcraft II: Wings of Liberty to play Blizzard's Dota, but Blizzard does have plans for some kind of monetisation of the game.