Steam's Big Picture mode was released out of beta recently, paving the way to their new "Steam box" console, which will compete with next gen consoles. Before the "steam box" was just rumors, but Gabe Newell recently confirmed that they were true in an interview with Jason Schreier, from Kotaku! Valve is hoping to release a gaming pc that will boot up directly to steam, which will, of course, be in Big Picture mode.
Gabe has a bit to say on the situation, including that other companies will definitely be releasing similar products soon. He also says the hardware will be much more controlled, as apposed to a normal pc.
You can read more of what he says in the interview here:
http://kotaku.com/5966860/gabe-newell-living-room-pcs-will-compete-with-next+gen-consoles