It's been confirmed that while the trailers so far were realtime demo sequences, the MGS4 trailer for TGS 2006 is a compilation of gameplay.
Also, from 5:55 to 7:04 in the same mp3, Yumi Kikuchi, one of the voice actors of MGS series and the radio hostess of "Hidechan Radio", watches the trailer and you can hear the sound (and her "oh" and "ah"). You hear roars of metal gears and gunshots. Though some cameras are modified for the trailer, Kojima says what she saw was real gameplay controlled by a player. According to Kikuchi and Kojima the movement of Snake in the new trailer is very inconspicuous and subdued (He's hiding in somewhere?).