State of Decay has become one of the most sold Xbox Live Arcade games in the entire history of the online Xbox LIVE service, making it's way right behind Minecraft in the XBLA charts and has been selling like hot cakes ever since it's release.
If you didn't already figure out that Microsoft are happy with the outcome of State of Decay by an appearance of a State of Decay t-shirt wearing Phil Spencer at last year's Xbox One reveal, then new information about a partnership with the development team should confirm it for you.
The developer of State of Decay, Undead Labs, has recently signed a multi-year, multi-title partnership with Microsoft, which suggests that there are going to be a lot of new zombie games from Undead in the next few years, and they will probably be exclusive to Xbox One.
Undead Labs previously had plans to make a zombie MMO similar to State of Decay, which had been named Class4, however this new partnership may put a halt to this development.
Alternatively, this could mean the developers behind State of Decay now have more time and reason to pursue developing Class4 for Microsoft, along with other titles.
Community manager Sanya Weathers was asked about Class4 and her reply was "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."