In Rich's source article, he questions the future of SteamOS and the partners involved in some of the ports are also questioning. Some people have started using past tense. I have no idea what Valve is planning, but my guess is that it's a long term play with limited resources. I'm guessing some of the interest inside Valve has waned.

Remember SteamOS was born before Win8 was announced and Valve was scared where MS was going. Steam on Windows seems pretty safe, the pressure is off.