Undead Labs' State of Decay has been a hit by all metrics. It's Xbox Live Arcade's fastest-selling original game, and it's been well-received by critics. The only thing that's missing and that players are clamoring for is cooperative play, which the developers have intended to release as downloadable content.
Well, those plans have changed. Undead Labs has confirmed to IGN that the co-op DLC is dead in the water. It sounds like the project was a bigger undertaking than Undead thought it would be, as the studio explained that retrofitting State of Decay to add that component would likely take the rest of 2013 and well into 2014.
However, the developers sound like they're far from done with the new IP. They promised that "co-op multiplayer will be the absolute heart of any future State of Decay games." I guess that's not surprising; games with this type of success rarely vanish into the ether.