The latest update of Bungie's official blog revealed that they won't be making any big announcements during the upcoming PAX gaming conference, although they are currently working on 3 new titles.
"For the record, we have no plans to make any big announcements or huge reveals at PAX this year", reads the official Bungie blog. "While we will have some Halo 3 multiplayer stuff for you to check out, this is not going to be the "big announcement" many of our fans are clamoring for. Rest assured that when the time is right, we will be making announcements and talking about the stuff we're currently working on. At the moment we do have three distinct projects underway within Bungie - some familiar, some not. Some on a closer horizon, some quite far off.
We know for sure that at least one of the aforementioned 3 titles is a new Halo game, as it has been confirmed during this year's E3.