In an interview with Valve Marketing VP Doug Lombardi, players won’t expect the title to arrive for a while, possibly until 2010.
“The next time you play as Gordon will be longer than the distance between Half-Life 2 to Episode One, and Episode One to Episode Two,”
Half-Life 2 arrived in November 2004, with Episode One arrive nearly two years later in June 2006, and Episode Two following in October 2007.
However the marketing VP offered a sort for consolation, noting that Valve “may [announce or show something] at the very end of the year.”
Valve is currently putting the finishing touches on its cooperative play zombie killer Left 4 Dead which is due out on November 18th while the studio provides updates for its multiplayer shooter Team Fortress 2.