OK so here's where we are at. Legit talk right now, folks.
- StarCraft just had a content release with Remastered. They will have a sort of 'annual design change' coming up, however. It looks like they're a focus of the Preview video on Monday. Probably won't be at the Blizzard Reveal Ceremony.
- Heroes of the Storm had a hero released recently (Garrosh), but tends to have frequent little content drops. It looks like it will be part of the Preview video on Monday alongside StarCraft, and as such won't be part of the Blizzard Reveal Ceremony.
- Hearthstone just had a massive expansion released about a week ago, and the next one will likely be announced at BlizzCon based on their usual content timing. So they probably won't be at the Blizzard Reveal Ceremony either.
- Diablo had the Necromancer DLC a while back, and there is nothing new coming out soon. They may or may not continue releasing small feature packs which didn't make it into the cancelled expansion. But as far as "Diablo 4" goes, which we know is in development, that's most likely still 1-2 years away from an announcement given that they only just recruited their Art Director about a year ago. Therefore also not likely to be featured at the Blizzard Reveal Ceremony.
- Overwatch has had some sort of map teased, and it's possible Jeff Kaplan will get on stage during the Blizzard Reveal Ceremony to talk about it for a bit. We'll also likely see that new animated short to go with it.
- World of Warcraft will definitely mention 7.3, but as far as announcements go, it's already very old news. Even its features. They will likely skim through the features and show us a trailer, however, at the Blizzard Reveal Ceremony.
So there you have it. TWO GAMES are likely to be represented at the Blizzard Reveal Ceremony. I highly doubt either of these games will require more than 15 minutes each, whether it's for the Overwatch map or 7.3. That leaves a bunch of time for something bigger. Like 8.0.
The expansion announcement is still very, very likely at this point.