While Blizzard are hosting a press conference this Wednesday in Cologne (at noon local time), that particular press conference will not be livestreamed (as far as we know). The big reveal, the new World of Warcraft expansion, will however be premiered and livestream on Thursday (the first public day of the show) at 17:00 BST (18:00 CET).
Blizzard (as per usual) have a rather massive stage schedule with cosplay competitions, tournaments and panels planned for the show - and you can check the details over on Blizzard's Gamescom site. Hopefully we'll have the livestream available here on the Gamereactor Live page on Thursday. At least we aim to have it.