Exactly. And why not put the players and developers on the same platform? It's a match made in heaven!
Moving toward an upstreaming, open-source, GNU/Linux platform means that not only do they have more fine-tuned control of everything, but also that there are _many_ more sets of eyes and hands to find/fix problems and to help contribute to the gaming and Linux ecosystem as a whole.
After seeing nVidia's CEO making his keynote for a new line of video cards on a Ubuntu powered laptop[1], I have no doubt that there are many companies other than Valve that see the great potential in this.
There were some rumors about Crytek and Unreal guys wanting to support Linux, too. With these latest announcements, I'm sure they will now, if they weren't going to do it before.
I'd say there is hope. Especially as most (and I'm guessing here) PC revenue comes from Steam anyway.