Blizzard is getting ready for some big news regarding Diablo III. A new site has appeared on the Battle.Net site called "Reaper of Souls". The quote comes from the Book of Tyrael and reads, "Death, at last, shall spread its wings over all."
Blizzard has promised a "big announcement" at Gamescom. Perhaps a D3 expansion? Judging by this site, that seems to be the case. We'll keep you posted as the story develops.