Have a quick look at Gamescom schedule / Stream stage.
http://gamescom.blizzard.com/en-gb/schedule
If you take a close look, all games are represented but the Diablo franchise on the Stream Stage.
Then we got this: https://gyazo.com/8566b2c665a039075d45558e27d35bf5
Diablo 4 / Diablo MMO? Or at the very least a Diablo 3 expansion (I personaly find this very unlikely).
Let the speculations and hype fly.. what are your thoughts?