Joystiq has just released a killer video teaser that about made me wet myself in anticipation.
From what they show in the video, we can expect snow level, S.E.A.L. levels, chopper insertions and a ton of other new and varied content for the single player.

For me, the COD series has always truly embraced the single player aspect and given a fantastic Multiplayer side effect from excellent level design and well balanced weapons and loadouts. I hope that it holds true and they develope a game that excercises a well scripted and immersive single player experience that we can play through to grasp the understanding of the weapons that we'll take into the MP battlefield.

Oh, the link :)

Here you go