Gametrailers say 250k for State of Decay:

http://www.gametrailers.com/side-mission/54029/xblas-state-of-decay-breaks-250000-copies-in-first-48-hours

edit: Yeah, Undead Labs website says a quarter of a million:

http://undeadlabs.com/2013/06/news/breaking-records/

http://forums.undeadlabs.com/showthread.php?19360-Breaking-News-And-Records-Wow-%286-7-2013%29

"North of 270k"

At 1600 msp, the game would have already made $5 million. The budget couldn't be much higher than that so I think the devs have already made a profit.

Well deserved IMO. One of the best zombie games to date.

Undead Labs

We have sold more than a quarter million copies since we released the game two days ago. State of Decay has smashed all kinds of records. The only game that ever sold more on XBLA this fast was Minecraft…an already hugely popular game.

There just aren’t the words to describe the feeling.

This was you. We did not have an ad budget. We didn’t have a physical copy to load onto shelves, no worldwide multimedia push, no studio reputation with millions of followers. All we had was what we believed was a great game and a great community. And make no mistake, a solid game is not enough, not in 2013. Plenty of great games wither away in obscurity. This train got rolling because you got out and pushed.

http://undeadlabs.com/2013/06/news/breaking-records/

Over 300k.
Going to sleep now and hope for another nice increase when I wake up.

One day later, 80k more. Awesome and now confirmed to be the second fastest selling game right after Minecraft and in front of Dead Rising Case Zero.

On top of that it's now also the best selling XBLA game of 2013.
Sold more in 1 week than Terraria did in 10.

The game is still waiting certification in several other countries.

Quite a few announcements already.

Summer of Arcade titles (August 7):
TMNT Out of the Shadows
Flashback
Brothers: A Tale of Two Sons
Charlie Murder

Minecraft Xbox One Edition (Going to be huge surely)

World of Tanks Xbox 360 Edition (also huge though going to be F2P)

Plus a couple of others.

State of Decay has now 450134 on the leaderboards.