From what i have been watching and playing, HS really needs a spike of go-juice. The next rotation of standard will change a lot of things but the next expansion really needs to hit a high note after Karazhan. D3 is entering a new state where the new season is not complimented with a really large batch of other things on top of the ladder reset as it will be only the reset. I really don’t think it will get that much of a new spike as it’s pretty old game already and it has had so much reworking done to it trough the years.
What i expect (and some of this is pretty clear):
Overwatch: Sombra and maybe a new map. Breakthrough how the new season has been going.
Diablo: Something that has to do something with Necromancers. Not a large scale expansion but paid DLC characters? Necromancer first and then they will bring some of the other old characters from D2. Paid storage space.
Hearthstone: New expansion. Explanation on how the next standard rotation will work out.
Warcraft: Hype about the coming raids? WoW is pretty much still running with oiled gears from Legion launch so i can’t see them having anything too big.
Starcraft: Maybe a new Nova pack or re-hype of the coop system. Maybe a look in to the future of the e-sports scene as things have been happening in Korea.
HotS: Overwatch themed maps? Brawl hype? I haven’t been following HotS for some time.
My wild guess is that they will announce Diablo game that is in the style of DS. DS3 being the “last of its kind” the time seems to be pretty ok to move on that market. First look streams 1 or 2 weeks after DS3 DLC to ride on the hype?