Blizzard have announced that the next World of Warcraft expansion will be announced during Gamescom.
The expansion will be announced on August 6th at 6 p.m. CEST. If you are attending Gamescom, they will be in Hall 7 of the Koelnmesse. You can watch it with them live. If you are watching the announcement live on the computer, a stream will be available at www.blizzgc.com.
The last World of Warcraft expansion to be released is Warlords of Draenor, which came out on November 13th 2014.