Its been quite some time that speculation of Valve's 'Steambox' might be a console. Gabe Newell confirmed a while ago that Valve's future is in the hand of its future console release. Newell also doesn't care for Windows 8.
According to German IT news site Golem [Google translate version], Valve engineer Ben Krasnow attended SSIM 2013 which was held in December and there confirmed that the company has a console-like piece of hardware in the works. He also reported that Valve is working on secret project for the console.
Rumor has it that the console will be revealed at GDC this year. It could possible that Valve releases Steambox with exclusive games like Half Life 3, Portal 3 & Left 4 Dead 3.