Valve may be developing a PC hardware spec to potentially package with Steam software in a "Steam Box" bundle, according to The Verge. Citing anonymous sources, the report aligns with comments Valve co-founder Gabe Newell made in an interview with former Ars staffer Ben Kuchera over at the Penny Arcade Report. The report is also supported by some recent Valve actions, including this patent for controller hardware last year.
If "Steam Box" rumors pan out, the software would be at the center of an open gaming universe that The Verge believes would be analogous to how Google handles Android. Actual devices may be made by a variety of partners (Alienware X51 is rumored to be working on an early version) and the underlying Steam Box software would be readily available to any company willing to partner.
Major gaming conferences such as GDC (this week) and E3 (early June) are coming soon, making the timing right for major announcements. The Verge has approached Valve about the rumors but did not have any official comments to share at this time.