The second of the three five-man dungeons in patch 4.3 is the Well of Eternity, which will see you and your four friends going back in time to get the Dragon Soul. You'll run into Illidan, before he turned into a villain. Wowheadnews has a bunch of screenshots for you to look at.
More screenshots can be found in the link below.
Links
Wowheadnews - 4.3 Preview: Well of Eternity Overview and Dragon Soul Testing
