Also, as you can see to the left, the actual official teaser poster for Transformers 3. Not really sure what is going on in that regard as the Prime poster is official in some capacity (someone with access to the Prime model to create it) and Hasbro is using it. For my purposes I consider one the Hasbro Teaser Poster and the other the Paramount teaser poster.
The leaked description is accurate, here is my summary.
Begins with words of July 20th, 1969 (date of the moon landing)
Apollo 11 traveling to and orbiting the moon.
Cut to words: "A Generation's Greatest Achievement"
Archival footage of landing and saying "The Eagle has landed"
Cut to words: "Our Nation's Proudest Moment"
Re-creating walking on moon with "One small step for man, one giant leap for mankind."
Cut to words: "A Secret Hidden for 40 Years."
While Walter Cronkite reports that Apollo 11 is out of communications range on the far side of the moon, Neil Armstrong and Buzz Aldrin are really investigating a crashed starship full of Transformers. Armstrong reports "the hull has been breached. Extensive damage. No signs of life or movement... You cannot believe what we are seeing. ...We are not alone after all...
Cut to camera traveling across the moon surface, to and through the ship, into a Transformers face (with "mustache"), and continuing into his eye and insides that change to the Dark of the Moon logo followed by the release date of July 1st, 2011.
Based on the brief images of dead Transformers, I suspect this is the Ark as the faces showed an Autobot structure. We saw the Nemesis marooned elsewhere (Mars I think) in Revenge of the Fallen and it had to have been fighting something. Based on the face and the mustache, I suspect the Transformers at the end of the sequence is Alpha Trion, one of the original 13 Transformers and protector of Cybertron. Thanks to Michael, V1p3rs and Rak33n for the YouTube links.
Update: Added link to HD version on YouTube (great for looking at full screen). I have the embed version above in HD also. If interested in screen captures, TFW2005 has posted many here.