Bungie have confirmed that Destiny: House of Wolves will launch on May 19. The new expansion will not include a new raid, instead it will add a new three player cooperative multiplayer arena mode, called "The Prison of Elders".

Patch 1.1.2 is now live and is roughly a 6GB download. This will contain most of the content for the House of Wolves expansion.

Source: http://au.ign.com/articles/2015/04/13/destinys-house-of-wolves-expansion-will-have-no-new-raid