Will you be able to run games that aren't on steam with it?
Non-steam games?
Considering you can just run those normally on your PC or console, and that the supposed Steam-Box is optimized for Steam, probably not.
You're asking to run standard PC games on a mini-PC/console specifically made to run Steam and Steam-based (most likely only Valve games at this point) games.
You might as well ask Valve to put together a normal size gaming PC, slap some steam logo stickers on it, and install Windows 7 64-bit with the steam logo as the wallpaper.