Valve has confirmed that they won't be making exclusive titles for their SteamOS or Steam Machines, and that they have no intention to "artificially drive consumers" to the platform.
Valve's Greg Coomer confirmed as much to IGN: "You won't see an exclusive killer app for SteamOS from us. We're not going to be doing that kind of thing."
Coomer then went on to outline where they feel Valve will be positioned in the future, and how they see it playing out: "We don't like to create those artificial barriers to accessing content. We believe that, in maybe five years from now, folks will find it a quite antiquated notion that you should assume that when you change devices or platforms, that you lose all of your other games and friends."
"We're hoping to unify, to get Steam to be as platform- and context-agnostic as possible. You shouldn't have to shed that every generation, or even slightly shed it."