Im txgrim4 (Grim, Grimmy, Grimsta), i have been playing xboxlive for 9 years, evr since day 1 of Halo:CE til now. I love H2, that and Halo 1 are my favs. Im a Halologist when it comes to the Bungie/Halo Universe. Ive also played Marathon Series, ONI, and Myth Series. I live in Texas, Play Football, and cant wait for Halo 4!
The following is a paragraph from http://www.xbox.com/en-US/Marketplace/Product/Halo-4 talking about Halo 4.
Halo 4 is the next blockbuster installment in the iconic franchise that's shaped entertainment history and defined a decade of gaming. Set in the aftermath of Halo 3, Master Chief returns to confront his own destiny and face an ancient evil that threatens the fate of the entire universe. Halo 4 marks the start of a new trilogy that begins with its release in 2012.
Notice that they use the word Ancient, to describe threat. Lets think of what all could be ancient:
Obviously the Forerunners, the Precursors, The Flood, any other things that could be older/ancient in the halo universe.
[Edited on 06.06.2011 12:55 PM PDT]