Wasielewski told GameSpot, "At GDC, they're going to have more information, and we'll be there. That's the official stuff we can say." Also, "Their controller is finalized. So now they're going to production and at GDC is when they're going to announce more stuff."
That seems to indicate that the last leaked image we saw of the Steam Controller (pictured above), with its pseudo D-Pad and Xbox-esque design, is probably pretty close to the final version. I was also speculating just the other day that the announcement of Origin's new Omega line of living room PCs was the start of Steam Machine round two, and that's seeming even more likely now.
One more interesting tidbit from Wasielewski's interview: He says that the "Steam Machine" name is "pretty much dead," replaced by the generic "living room PC." I'd always thought of Steam Machine as a designator for the fact that it runs SteamOS though, so I'm torn. Steam Machine is definitely more convenient than "Valve's new SteamOS-enabled living room PCs." Try saying that three times fast.