On their official website, Undead Labs has revealed that after being in an alpha stage on Steam Early Access since late September, they are getting ready to launch State of Decay officially on Steam. The official opening day will be on Tuesday, November 5th.
They note that they will continue to make improvements to the game after launch, and on launch day they will be doing some "serious celebrating" with contests and prizes and more. They also request that players continue to supply them with feedback on bugs or feature requests for the game.
You can check out the game at the source link, and here's a trailer for your viewing pleasure.