The new Weekly Update bluntly admits that skulls WILL be in Halo 3, and hints (I inferred hopefully, don't quote me) that they'll be "active" via online co-op and perhaps even a menu once you've discovered them. Looks like some classics are back along with tantalizing new-BLAM!-comers, so head over to HBO for all of your latest Halo 3 news.

POTS! Holy hell, how are you holding up?
o.O Hey POTS.

Secondly, I knew it! We found alternate menus in the Halo 3 Beta, I knew there'd be more!
Remember Remember the 25th of September. xD