I spent more time than I should have on this, so it is going on GAF as well as AJ
So basically we have very few options as to how this campaign expansion is going to be released.
It appears completely plausible that the new campaign experience, along with all the new maps will be available via DLC. The Oblivion expansion was over 1.5 gigs so any size limitations you might think there are would be squashed via this precedent.
The real question appears as to what the disks on the shelves will contain and at what cost. Unverified tests show there to be nearly 3.5 gigs left on the Halo 3 disk. This would leave room for 6 new maps, 1 gig, and a campaign extension, 2.5 gigs. If Bungie went with this option, I could reason a selling price of $60. Each map pack has sold for 800 points, about $10. The current selling price of Halo 3 is $50, and the fact that this game is 1 year old, -$10. Bungie and Micro$oft would have to swallow the fact that every currently unsold and pressed disk of Halo 3 would be majorly devalued at the announcement of this expansion disk. This would be tough, coupled with the unknown of the space restriction and this seems to be an unlikely scenario.
Another possibility is, following the Halo 2 post launch map pack disk release, a separate disk containing all after-launch maps and the campaign expansion. Estimated cost at around $40, $20 for the new maps and $20 for the campaign expansion. This disk would then be loaded on your HDD and only be playable with the Halo 3 disk in the drive. Abuse would quickly arise, as in Halo 2, where the disk would be passed around to be loaded on several xboxs. It is possible some sort of access code could accompany the disk, like most modern software packages, to protect Micro$oft from losing out on much needed revenue (sarcasm added).
The last option would be an exclusive DLC release. This would really create a surge in sales of all the unsold copies of Halo 3 on the shelf. Those who play Halo 3 regularly are going to be downloading this expansion no matter what the disk choices are. If Bungie is planning on a making a new game, which we all assume they are, they would want to get every copy of Halo 3 off the shelf and into a console that they possibly could before announcing this new game. What better way to do that than with a price drop and campaign expansion only available through DLC? They drop the price of Halo 3 to somewhere around $40, charge $15 for the campaign expansion via DLC and continue with their current $10 a pop for each map pack. Include the silver membership with the purchase of the game and you have a recipe for something that could bake some money.
