Steam for Linux entering private beta in October for just 1,000 users
 

Next month, Valve is inviting 1,000 fortunate gamers to take part in the first external beta test of Steam for Linux. The trial includes the service itself and one game (which we're taking to be Left 4 Dead 2) that'll run on systems running Ubuntu 12.04 and above. Users won't get their hands on any other Valve titles, or Big Picture Mode, and the company is asking that only experienced Linux users get in touch -- novices are politely asked to wait for a subsequent release. It'll offer up details of how to sign up shortly, and given the love for the Valve's other products, we suspect it'll be a little oversubscribed.

http://www.engadget.com/2012/09/27/steam-linux-beta/