There are 200-300K people playing halo every day online at any given time. the number goes to 500K on weekends... This is a smart move by bungie...

I finished yesterday Half-Life 2 (360 version) in 9 hours. Call of Duty 4 was even shorter.

Okay...

I wasn't saying it as a bad thing.

But I hope that people don't expect another ten hours from an expansion of a game, when it'll be more around 4-5 hours, which, btw, is fine.

^^I don't know, they could theoretically make another campaign just as long as the original game, but without any multiplayer outside of coop. Not having multiplayer would allow them to allocate many more resources to the campaign, which could allow them to make a campaign of similar length in a much shorter time.

I like the look of that, though I dont really get how that will fit in with Halo, it seems a completely different art style

Found some evidence that it may be a prequel: Look at the right corner at 0:18. It says '2552', and Halo 3 is set in 2553. It could be a 'mid-quel' of sorts, actually, since I believe Halo 1 was set sometime in 2552 (though there is only a difference of a few weeks between the three games).

So, it could be something going on at the same time as Halo 1, after it, or earlier in the year.

This is all assuming that the '2552' means anything.

It will help sales because Bungie can include this in a new Halo 3 GOTY version that can drive sales.

Need proof that it helps? Look at COD4 and Oblivion when they added free expansions. It really helped. Heck, even now, Oblivion is still selling 5,000+ units in NA for the GOTY version at $59.99 with the Shivering Isles expansion pack.

One theory was that it involves the ODST's fight on Earth between Halo 2 and Halo 3.  That might explain the date difference?  I could be wrong because I don't follow Halo canon too closely.

Maybe you will get to play as he Covenant? Or just a normal marine or citizen?

It will help salos of Halo 3 undoubtedly, but I highly doubt it will spur console sales as someone mentioned.