While State of Decay continues to sell thousands of copies on Xbox Live Arcade, plans for a PC release are still intact. In fact, Undead Labs has confirmed that the game will be heading to your computer later this year.
According to the developer, the game will take place in the Steam Early Access program before release. I should note that an advanced version of the game will only be playable with a traditional controller. However, the final PC release does allow for a mouse and keyboard setup.
Specific dates will be mentioned in the near future.
Source: Undead Labs Forums