At the time of this writing speculation continues to run wild within the Bungie Forums. Popular theories point to new campaign levels, a map pack retail disc with a new cinematic (as seen in Halo 2's map pack) or an entirely new title within the Halo Universe, specifically due to references of the MAC weapon. Some of the more interesting tidbits could easily be gleaned from scanning the string of text (available after the break). The primary, DARE, is given a code number which ends in S1 leading some to believe the string of text occurs prior to Covenant attacks during the SPARTAN-1 era (yr.2491) -- way before John-117 joins the program in 2517.
Which theory gets us excited? The mention of squads could point to a pre-Halo era tactical shooter in the original SPARTAN phase that led to the creation of Master Chief. Wild thinking and speculation but we can't wait to see where this one is going.
[Thanks to everyone who sent this in]