The clip merges in storyboards and has no lip-synching to the dialogue, indicating it's something in the early stages of production. But the voice acting is a close match to what we've heard already in StarCraft II: Wings of Liberty, and the fact this disappeared from both YouTube and Vimeo on copyright claims lends credence to it. That said, Heart of the Swarm has no release date set, and even if this is authentic, you just can't tell if what you see here is in fact how the story will play out in the final product.