As for what the reveal could be, we've got a handful of ideas. Two teaser transmissions on the other main Bungie page, including one from The Superintendent that talked about Tokyo (it should be noted the Tokyo Game Show is next month) and another from a soldier under fire. We know Bungie is working on at least "three distinct projects," although one of those could've been the recently-released Halo 3 Title Update 2. One of those is a new Halo game unrelated to the Peter Jackson project (could it be Halo Recon Advanced Warfighter?).
Other potential candidates include HaloCon, a Superintendent Xbox Live Arcade title and/or the Mythic map pack dates. Or could it be something completely different. Or it could be nothing at all. Again. Let's hope it's anything but the latter. Update: Commenter Edward Dean below shows us what is purported to be a picture from inside Halo 3 that teases a teaser for a new game tomorrow. We're trying to confirm its validity at the moment. Picture after the break.