We know it's coming, but Blizzard wanted even more promotion to build anticipation.
Yes, all you World of Warcraft players know that the huge 5.4 update is coming tomorrow. But Blizzard's marketing and PR departments obviously feel not enough people know its coming, so they have produced a narrated video to re-emphasize all the changes coming in the patch.
From the Timeless Isle to Proving Grounds to the Siege of Orgrimmar Raid instance, the video lays everything out, as well as providing some nice scenery of what everything will look like. It also offers a few more details, including that the Siege will take place below Ragefire Chasm.
Also, the Timeless Isle will appear off the southeastern portion of Pandaria near The Jade Forest. And it will be fairly easy to get level 535 gear, as well as upgrade tokens for your alts.
My personal favorite is the flex raiding. But enough talk ... er, writing. Watch it for yourself.