Although Xi3 nor Valve have confirmed that the Piston is the Steambox (while substantial evidence suggests that is it) an image posted by Infinity Ward on its social media channels suggests that it might be.
The image posted by Infinity Ward doesn’t give away any details about the box, and only has the comments “Game development” and “What’s this?”.
At the Consumer Electronics Show in January, Valve and compact PC manufacturer Xi3 announced the Piston, a first-stage development computer that’s been optimized for Steam. As Hardware Canucks reported in January, the Piston is based on Xi3’s compact X7A modular system. When bought directly through Xi3, the X7A typically comes equipped with a custom mini ITX motherboard, AMD’s embedded R-Series APUs, an integrated 384-core 7660G graphics processor and 8GB of memory.
While the Piston could be the Steambox, or a Steambox, in order for the strategy to work Valve needs to convince developers to port to Linux and OpenGL.