Captain's Draft will have two teams, each of which nominates a captain, take turns banning, picking and counter-picking heroes from a randomized pool of 24. The new Armory will let you filter items by attributes like quality, rarity and type.
The Dota 2 store will also be receiving an update with First Blood, which includes new community-created content and a Portal Pack. The Portal Pack will include an Aperture Science-themed HUD skin, some "Wardcores" (wards made to look like Aperture Science cores) and the aforementioned GLaDOS announcer voice.
Unfortunately, no cake was mentioned as part of the First Blood update. If anyone tells you there's going to be cake... well, you know by now.