User blog comment:KATANAGOD/Treyarch Teases Zombies on Facebook/@comment-4312627-20120914015522/@comment-356904-20120914162228

"MW3 was just an overhyped map pack for MW2."

It may not be explicitly so, but...

http://i15.photobucket.com/albums/a383/jonnierose/Clipboard01.jpg