The next World of Warcraft expansion, Battle for Azeroth, was announced at Blizzcon.
https://worldofwarcraft.com/en-us/battle-for-azeroth
Additionally, Blizzard is apparently launching World of Warcraft Classic (a "classic" server, or servers) at some point. There don't seem to be many details on this yet.
https://www.youtube.com/watch?v=TcZyiYOzsSw