Mike Morhaime, Blizzard co-founder and president, has said the studio will be "sharing more Diablo-related news" at this month's Gamescom event in Cologne, Germany.
A Blizzard press conference is scheduled for August 21st at 11:30am CET (10:30am UK, 2:30am Pacific). An expansion was confirmed to be in the works back in November 2012.
Diablo III spreads its own wings September 3rd on Xbox 360 and PS3, with PS4 in 2014. Visit the teaser site.