The original release date was to be June this year, and from the sounds of things, they might be on track

http://www.co-optimu...hadow-fall.html
"New details haven't emerged, but we know Killzone: Shadow Fall will feature four player wave-based co-op. The co-op will be entirely online with no local functionality, and there won't be a co-op add on for the campaign. Season Pass holders will have access to the Co-Op Expansion Pack when it drops, and others will presumably be able to purchase it separately. "
So for those hoping for a co-op campaign or story mode, looks like you might be outa luck. But for the fans of horde/wave mode co-op, its on
In early April GG tweeted it was still under development, then later tweeted it was in testing!! So sounds like they are on track for June



