Battlefield 3. The footage apparently shows U.S. Marines engaging PLR forces (i.e. "the baddies") in Iraqi Kurdistan.
The trailer also confirms the previously rumored "Back to Karkand" DLC, which comes included with all limited edition (first-run) copies of the game. The pack contains four Battlefield 2 maps that are "re-imagined" with Frostbyte 2's "physics, destruction and visuals" -- similar to what DICE did for older maps in Battlefield: Bad Company 2. For those who don't pick up the limited edition, you can expect Back to Karkand to become available for purchase sometime after Battlefield 3's launch this fall.