Hearthstone also has two panels at BlizzCon 2015: "What’s Next" and "Fireside Chat." There are many hopes that Blizzard will show a new piece of content for the game, and if the current trend continues, it will be a new solo Adventure (the other two are The Curse of Naxxramas and Blackrock Mountain). Its official release can be expected somewhere in November-December this year, and we will likely find out about all the details during the "What’s Next" panel.
In addition, during the "Fireside Chat" the developers will sum up a few last months of the state of the game. In particular, the official schedule includes notes on the team speaking about the process of creation of various Tavern Brawls and answering questions.
In general, the upcoming BlizzCon should be quite interesting. It would be naive to expect any major announcements, and most likely we will simply get to learn more details about the expected projects that have been already announced by Blizzard. Nevertheless, it’s a huge event and we know we'll all be watching it.