After exciting announcements back at CES and the Big Picture beta, Gabe Newell came forward in a BBC interview explaining a bit more about the upcoming Steam Box. While actual release dates are still unknown, prototypes for Valve's version of the Steam Box are heavily in the development stage, and will hopefully be in the hands of select customers within the next three to four months.
The main hitch that is holding back the Steam Box seems to be input devices, namely controllers. Gabe mentioned how biometrics will play a large role in gaming, allowing things such as heart rate to be taken into account. This sort of information helps developers better understand how to synthesize the experience they want, such as a horror game's input being built right in order to not hinder the player experiencing the maximum fear any game can give. To address this, Gabe mentions how these prototypes will come with multiple prototype controllers that will allow Valve to gauge which controllers perform best, and where they can then be improved for a more perfected input device.
While Newell still shrugs off any questions of Half Life 3 or Portal 3, he does mention that Valve is constantly looking over their IPs, even the less known such as Ricochet, and questioning how or if the proceed with them. We don't know if any of these games will make an appearance any time soon, or ever for that matter, but it is clear Valve is hard at work to push the gaming industry in a new direction, and we can hope to hear more about the Steam Box as those few months pass.