"Blizzard: The Game" as Mike Morhaime named it marches ever on toward release. Heroes of the Storm will be entering closed beta on January 13th. The difference between this and their current technical alpha, which is also invite only, will be a ramping up of frequency of invites and more polish in various areas. This was the most major of Blizzard's announcements for the game during Blizzcon, but they detailed some other upcoming changes.
Competitive play spent the most time being discussed. They're gearing up to include both a draft mode and ranked play. The draft mode functions similarly to other MOBAs, two teams picking from a shared pool of all the heroes in the game and allowing no duplicates. One differences is there's currently no plans for a banning phase, due to the size of the HotS roster. This was rightly questioned by an audience member during Q&A, pointing out that tournaments have a 1 ban per team system. Lead Designer Dustin Browder reiterated that they'll keep tracking it and that this is only for their online ranked modes, rather than a global rule for tournaments.
That ranked play was another announcement. It comes in the form of leagues which are most closely styled after Hearthstone's ranking system but with an ELO-like player rating that governs how many points teams will earn. There are two seperate leagues, one for solo players and teams smaller than five, and another just for 5v5 matches between pre-constructed teams. You'll advance from rank 50 up to rank 1, seperated by tiers of points that are earned and lost via matches.
Also mentioned quickly and playable on the show floor were four new heroes including Warcraft's Jaina, an ice mage, Thrall, an orc shaman and the undead elf ranger Sylvanas. Last was The Lost Vikings, the titular protagonists of one of Blizzard's older games. They operate as three separate characters on the battlefield and can split up or team together as necessary, similar to Dota's infamous Meepo. There were also new battlegrounds shown off, which can be seen in the below trailer: