Damn computer gave me problems right when I was trying to download so I had to restart - damnit!
Anyways, I dunno how many teasers have to be released before people on here get the point and realize what a teaser does - TDG already beat me to it, but people are crying that they got teased by...
...a teaser.
And there was plenty of info from that I could tell, as others have noted as well...
It's definitely New Mombasa as a few things said directly in the video, the tether is either still up, meaning that it's right before the Chief got there, or it's another one/new one, going on at the same current time as the events in Halo 3...
What it ultimately looks like is that they are giving something special to the fans that wanted to play that E3 level, or wanted to continue in New Mombasa, by letting us play on as ODST's as the Chief left - either in first person as an ODST itself, or through the eyes of this A.I.
Great teaser that managed to show loads of info that fans will find, and I can't wait to see the results of the massive dissection that this video will get...