More info already:
http://vividgamer.com/2011/12/12/half-life-3-arg-may-have-begun/The following are a list of clues that have been gleaned from the video:
A series of Greek symbols (СПУТНИК НАБЛЮДЕНИЯ <<ЛАНТАНУМ>>) can be seen above Wheatley. Translated, the message reads: Observation Satellite “Lanthanum”. Lanthanum is a periodic element in Group 3.
Translated back to Greek, “Lanthanum” reads λανθανω. Note the lambda symbol, a gaming icon that screams Half-Life.
Numerous constellations can be drawn in the stars behind Wheatley, all forming lambda symbols.
Wheatley finishes his speech by attempting to give coordinates of his location in space. He only has time to say “1, 1, 1″ before being cut off. 1 + 1 + 1 = 3
The atomic number of Lanthanum is 57. 5 and 7 are the starting and ending dates in July for next years E3. 5 + 7 = 12. 6/5/12 – 6/7/12.
Images of what appear to be a Headcrab can be captured within the video’s final second.
