It looks like Valve's not totally ruling out making its own version of the retail Steam Machines that so many other PC manufacturers are making currently. During Valve's press conference this evening at CES 2014, company head Valve Newell said, "We're gonna make that decision as we go along." when asked whether Valve would make its own retail Steam Machine. "We have plans to build more machines as customers ask," he continued.
So far, only 300 lucky beta testers have the Valve-made Steam Machine. Newell said that part of Valve's reason for being at CES was to solicit feedback from press and consumers, so it sounds like a Valve-made box might be more than just a dream for now.