I would have assumed something on the front page would be posted if Yogg had been found before. I might have missed a thread somewhere showing this, and if so, I'm sorry. Kinda new around these parts.
This youtube video shows some PTR screenshots of me Eagle Eyeing around Ulduar.
The macro for Eagle Eye to chain cast like Far Sight is /cast !Eagle Eye. Any Hunter or Shaman who wants to test this is free to.
As Blizzard states in the description of Ulduar, Yogg-Saron is supposedly under the structure. From what I see, this statement has more importance than one might make out to be. His "lair" sits below his prison, separate from the rest of the instance.
As far as I can tell, you can't get to his chamber by normal means. He must teleport you in once you reach his prison.
This is how I envision Ulduar working, from what I saw Eagle Eyeing around the instance:
1. Vehicle part before the Antechamber. 3 potential bosses exist out here. The Fire Giant, Voltron, and Razorclaw. (An area is designated for Razorclaw, so I assume he is some kind of boss.)
2. Slaying of the Titans in the unlocked area of the Antechamber. Thorim's Room and the Iron Council come after the Titans.
3. The Tram will not function until the Antechamber's bosses are finished off. When taken to the Spark of Imagination, another boss encounter will occur. The big red button must activate the giant door with the gnome's head on it (much like the final fight in Gnomeregon).
4. The Door opened by the button leads to the Descent into Madness. At the bottom, in a room filled with shattered stained glass, players will likely fight the Faceless General. (Players can currently explore the area that looks to be for him.)
5. Upon entering the broken prison of Yogg-Saron, players will be teleported to his lair below the prison. Yogg's fight must play off Insanity. The three chambers in Yogg's true lair possibly mean that Alliance soldiers, Deathknights, and Black Drakes will attack players during the fight.
That's my best guess, but it is speculation off of what I have seen. We'll find out what truely happens in 3.1, but until then, I hope I have brought you early pictures of Yogg-Saron.
CLICK THEM FOR LARGE PNGs WITH THE HEAD CUT OUT.