Well, Blizzard has now officially (as opposed to earlier leaks) released the schedule for Blizzcon next month. As it stands, World of Warcraft: Legion could really be the headliner, with four panels. Likely, because of the Gamescom announcement, we aren't going to have the same comprehensive set of panels we've gotten in previous odd-year Blizzcons, as we already know the headlining features.
WoW will have a "World and Content Overview" panel, a cinematic panel, a Game Systems panel, and a Q&A. My hope for the first of these is that we'll get a better sense of the patch release cycle for Legion. I don't think it's a terribly controversial statement to say that Mists of Pandaria handled patches a whole lot better than Warlords. Giving us a roadmap for the future of the expansion (preferably a big one you've got to unfold a bunch) would do wonders to mitigate fears that the future of "short expansion cycles" means anemic expansions. The cinematic panel should be fun, though not really about in-game stuff. Game Systems, on the other hand, could extend to a ton of features. I expect we'll be learning about how the Demon Hunter will function as a class, and also what's going to happen with the various class revamps, like Survival Hunters going melee. Personally, I'm very interested in seeing how Demonology adjusts to the loss of Metamorphosis (which is currently the heart of the spec) and also how much they'll lean into the "pirate swashbuckler" archetype for Combat Rogues, as that might actually get me interested in playing the spec.
There is no specific class panel, though, so it's possible this panel will focus more on larger systems, and we'll just have to wait for the beta patch notes to see what's in store. Given that Blizzard announced Legion will go into beta this year, I'm hoping we'll get a beta start date, though if it has to start in January, I won't be terribly surprised (no later than January though, I hope.)
On the Diablo III front, there's not much. I actually expected there to be a new expansion at least announced by now, but it really doesn't seem like there's enough to support that this time around, with just one panel called, generically enough "Dev Talk." Reaper of Souls did a ton of good for Diablo III's systems (and Westmarch is a really cool setting) but I think it's time for a new story/setting and hopefully class.
Starcraft II has a couple panels, but the intriguing one is "The Future of Starcraft II." The SCII model was to basically have oversized campaigns, but effectively really only cycle of campaigns between the three releases. The Future might simply be to talk about Legacy of the Void, but I imagine they want to keep the SC train rolling, given how big an esport it is.
Heroes of the Storm and Hearthstone are both on a much faster cycle, so I suspect we'll just get a preview of what the next few months will bring us. New card expansions, new heroes, and new battlegrounds are what we'll see. I don't know if we're going to be getting any world-shaking announcements.
The Overwatch beta is coming relatively soon, I think, but I wonder what we'll be seeing for that. There are two panels, one that's just "What's New" which I think is basically "the whole game." The other is the "World of Overwatch," meaning I think we'll be seeing more of the lore behind the game.
Personally, what would attract me to Overwatch is some kind of single-player or at least PvE content. I'm ok with Heroes of the Storm given that it's kind of in that Smash Bros. category - it's all about smashing your toys together. Given that Overwatch is this whole new intellectual property, I'd be much more interested in exploring it through a campaign, rather than reading stuff outside of the game that kind of contradicts my having Tracer fight alongside Reaper.
Obviously the thing I'm most excited about is WoW news, and hopefully the imminent start of the Legion beta. We've still got over three weeks to wait, though, so sit tight.