There is a hot new rumor today that Sony and Guerilla Games have secretly completed a playable demo version of Killzone 2..... and Sony plan to release the demo before Microsoft release their Halo 3 Beta!
Quoted from Luke Smith's Blog at 1up:
"Rumors pointed at the game's intended resurgence at their pre-launch Gamers' Day event last year. Ultimately, if the rumors are to be believed, Sony shelved showing Killzone 2 in favor of spotlighting Insomniac's new shooter franchise (and it will be a franchise) Resistance. The same rumors have pointed to Killzone 2 being much further along than previously expected -- with the apex of the rumor arc concluding that the game has been playable online for almost a year."