Undead Labs is waiting on Microsoft to greenlight the sequel to the open world zombie survival game State of Decay. Along with releasing a PC version of State of Decay and adding new features which include a sandbox mode, co-op, and multiplayer, (Update: Sadly UndeadLabs has announced that State of Decay will not have co-op or multiplayer, but the good news is any future State of Decay games will have multiplayer and co-op built in from the start) the developer is working on an MMO. Class4 will be set in the same universe as State of Decay and will take at least a few years to develop:

"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.

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."

For more information about State of Decay, check out the official site.