Yesterday Gabe Newell did an ask me anything (AMA) session at Reddit. The Valve co-founder answered a couple of dozen questions from fans, most of his responses were short but there were some interesting tidbits here and there.
Among other things, Newell confirmed Valve is using Source 2 as its primary game engine:
We are continuing to use Source 2 as our primary game development environment. Aside from moving Dota 2 to the engine recently, we are are using it as the foundation of some unannounced products. We would like to have everyone working on games here at Valve to eventually be using the same engine. We also intend to continue to make the Source 2 engine work available to the broad developer community as we go, and to make it available free of charge.
In response to a question about Newell's take on the direction Valve should take in the future, he replied "creating experiences" is one of the big things right now. Furthermore, Newell also sees some opportunities in artificial intelligence, and noted that he's personally looking at research in brain-computer interfaces.
The big thing right now is broadening the range of options we have in creating experiences. We think investing in hardware will give us those options. The knuckles controller is being designed at the same time as we're designing our own VR games.
Much more narrowly, some of us are thinking about some of the AI work that is being hyped right now. Simplistically we have lots of data and compute capability that looks like the kinds of areas where machine learning should work well.
Personally I'm looking at research in brain-computer interfaces.
Newell said he sees Portal 2 as Valve's best single-player game and that Dota 2 is his favorite multi-player game. He danced around inevitable questions about Half-Life 3 claiming "the number 3 must not be said" but did confirm that Valve is working on new IP set in the Half-Life/Portal universe. It's unknown if this means new games, it could be he's referring to the movie collaboration with J.J. Abrams, which he confirmed is an ongoing process.
One thing he did reveal about Half-Life is that it's a series he looks at with regret because he was too involved in the development. Newell adds that it's easier to be a fan of something he was less directive in:
The issue with Half-Life for me is that I was involved in a much higher percentage of the decisions about the games, so it's hard for me to look at them as anything other than a series of things I regret. There's no information in my response about what we'll do in the future. It's simply easier for me to be a fan of things that in which I was less directive.
Furthermore, he also hinted Valve is working on a VR game and vaguely responded to a question about a new Left 4 Dead sequel that Left 4 Dead is "a good place for creating shared narratives".
On a related note, Gabe Newell made it into the Forbes 400 list. Valve is a privately-owned company so it's hard to estimate how much it's worth, but the magazine estimates Newell's stake is worth $4.1 billion. This makes the Valve co-founder the 134th richest person in the world and the 47th richest in tech.