Update: State of Decay has now passed 500,000 sales on Xbox Live, and there's a PC version actively in development for Steam, which is unusual for a Microsoft Studios XBLA game. It's not clear who the publisher will be on Steam.
The XBLA version will continue to evolve over time as well. "For a start," said Undead Labs, "I can tell you we're working on a sandbox mode designed to be a pure survival simulation."
Original story: Despite State of Decay's rampant success on Xbox Live, the MMO follow-up, codenamed Class4, isn't a done deal.
"We cannot begin working on Class4 without a greenlight from Microsoft (who owns the IP, as part of the bargain that led to the funding and development of State of Decay) and a mutually agreeable contract," Sanya Weathers, director of community, explained to me.
"We have to agree on where we think the technology is going to be in a few years (since the game will take a few years to develop); we have to agree that we have the same goals; and we have to agree on how we'll collectively run and support the final game.
"Those discussions are still in progress."
State of Decay is an open world zombie sandbox tour de force, declared our Simon Parkin, and an Xbox Live Arcade exclusive. Word of mouth and a successful Undead Labs-run PR campaign helped the game become the second-fastest selling XBLA game ever, shifting some 250,000 sales in two days.
There have been some teething issues with State of Decay, though - Title Update 1 didn't work properly and Undead Labs has had a stressful time, by the looks of things, repairing it.