Game Informer has stated that the article on Halo 3 transcribed by a forum member and reported across various sites was in fact true, and not an April Fool’s joke.
The article claims that Forerunner will have “huge persistent worlds” created with an adapted Halo 2 engine. It also says the game will have co-op for up to four players.
Bungie claimed the article was “an April Fool’s gag” on their message board, but the most recent edition of the Game Informer mag has stated the opposite is true.
Those elves in that rumor mill are working very hard with this game.