Allnets on B3D is one of the few known pixel counters on the web and posted this about the X1 version of AC4:
http://forum.beyond3d.com/showpost.php?p=1803609&postcount=3775
Anyhoo, as far as I can tell from the XO footage of Assassin's Creed IV the other day, it's 1600x900 w/ their post-AA stuff.
So yeah I wouldn't take it as gospel just yet I believe he was working off a crummy video, but those are his preliminary findings.
For me I actually count this as a victory (even assuming PS4 is 1080P). The visual dfference between 900P and 1080P wont be that ,much, and at least 900P is a nice improvement on last gen. It's the 1080 PS4/ 720 X1 games (so far just Ghosts I guess) that bother me.







