Update: Microsoft has confirmed that Halo 3: Recon will be a full retail DVD release and it will not require the previous Halo 3 title to play. No official word yet on whether the title will be offered as a DLC as well.
Shooting straight from Microsoft's Keynote at the Tokyo Game Show, Bungie finally reveals details after months of teasers regarding the new Halo 3 campaign. Titled as Recon, the upcoming addition will be a prequel to the events of Halo 3 where players will unload on some Covenant fiends as a UNSC recon soldier.
This brand new hero set on a "new campaign" is expected to arrive in Fall 2009. Make sure to check back for more updates from this year's Tokyo Game Show.