Found by a user on NeoGaf yesterday, it appears that as of September 29, Valve has filed a trademark for Half-Life 3. According to a number of people on Reddit with much more knowledge about trademarks than I have, this means that Valve has 3 to 5 years to do something with the trademark before the rights are lost. Not much else is known about it really, just speculation in the threads. We will definitely bring you more information as it comes along.
Could this be Valve’s Steam Machine exclusive in an attempt to build their consumer base right off the bat?