Yeah saw this a few days ago in a news feed thing on my phone. Seems interesting.
Also... nice find braindancer. It would be nice to get another XCOM game. The first thing I thought of when I read what you wrote was "XCOM: Apocalypse?", because that was a city based game after all. On UFOpaedia I also read that the some downloadable pdf uses a font known as "XCOM-Regular". Also, the Advent site does also mention "We are still watching" at times, which might be relevant. Because in XCOM: Enemy Unknown/Within the voice that at times gives you special missions, and tells you how well you did at the end of a month in the game, does always say "And remember. We will be watching".
Although... so far we do not know if it will be an XCOM or not... Some have speculated that it might be a new Bioshock. Although, the XCOM stuff seems to be a stronger lead. It could of course also just be a compleatly new game, unrelated of both XCOM and Bioshock... or heck, it could maybe be a XCOM+Bioshock hybrid kind of a thing.
The fact that it is 2K that is releasing the info about this Advent thing does make me think that it might just not be Firaxis XCOM related though... since if it was it would seem more logical that it would be Firaxis that would be releasing this information. So if it is not Firaxis XCOM related... and if it is more 2K XCOM related... then it might be related to the other XCOM game. You know... The Bureau: XCOM Declassified. Which of course was not as well rechieved as XCOM Enemy Unknown/Within.
The images and such seen on the Advent page does not make me think of a 3rd person shooter type of a game though... they make me more think of Firaxis XCOM and the original UFO/XCOM games.
Who knows. I will atleast be keeping my eye on it (they have done a good job in that sence), and hope that it is a Firaxis and/or original UFO/XCOM game related, rather than 2K XCOM or Bioshock related (Bioshock was/is an allright game series, but nowhere near as good as UFO/X-Com/XCOM games in my opinion).