Bungie has announced that today's scheduled patch deployment for Destiny has been delayed. Update 1.2.0, one of the two pre-House of Wolves patches, was originally due out today around this time, but was pushed back for undisclosed reasons.
Our patch schedule for House of Wolves has changed slightly. 1.2.0 will not deploy today. Please stand by for more information. Game on.
— Bungie (@Bungie) May 12, 2015
Update 1.2.0 was technically released last week, but Bungie has yet to actually activate it. Bungie hasn't released patch notes for it yet, but did say it will consist of "final preparation and world changes" for House of Wolves.
Once the patch does go live, Bungie will presumably provide official patch notes.
Meanwhile, a second update, 1.2.0.1, is sheculed to arrive on Tuesday, May 19th, the same day as House of Wolves. This update will include the "final delivery and activation of Expansion II."
Destiny Expansion II: House of Wolves is the second of two planned expansions for Destiny, and is included as part of the Destiny Expansion Pass which is priced at $34.99. Alternatively, the expansion can be purchased individually for $19.99. With it comes all new content, including new story missions, three new competitive multiplayer maps, and a new cooperative Strike. It also brings The Prison of Elders cooperative end-game arena activity for Guardians to take on, as well as the Trials of Osiris for those of you who prefer PvP.