That's assuming that just because they're working on wearable computer hardware that they aren't also working on a console. Actually, reading between the lines, I see this linux support news as more proof that they're working on a console.
Here are some possible reasons why Valve might be working on linux:
1) They think win8 is so bad users will leave in droves to OSX and Linux. I doubt this, Windows has made a ton of mistakes before (ME, Vista?) but it's still king of PC. A lot of people were happy with 7. If win9 totally bombs as well, then I'd say the gig is up.
2) The monetization story has changed. The humble indie bundle has shown that linux users will pay for games and play them on their linux boxes. Is this enough for Valve to change their stance since for the longest time they've said it didn't make economic sense?
3) Valve is working on a console and won't (can't) pay to license OSX/Win as the OS and is smart enough not to write one from scratch. This reason makes more sense to me. Getting steam client working on linux desktops is just a secondary benefit of their primary goal: getting the software stack for their console.
It could also be as simple as them hedging their bets.
We are in turbulent times as different form factors , OSes , development methodologies and paradigms are competing for slices of the computing landscape. There will be some winners and losers here.
If you had to pick 1 platform that will still be around in some form or another 10 years from now regardless of what happens then Linux seems like a safe bet.
Putting in the groundwork by porting steam/source to Linux now could serve them well in years to come if they do decide to develop a Linux based console (or someone else does).
Tying yourself to just the Windows or OSX platforms could seem risky for a large developer.
I'm sure they would love to have Steam for iPad too but I can't see Apple letting them do that so they will do Linux instead.
Here are some possible reasons why Valve might be working on linux:
1) They think win8 is so bad users will leave in droves to OSX and Linux. I doubt this, Windows has made a ton of mistakes before (ME, Vista?) but it's still king of PC. A lot of people were happy with 7. If win9 totally bombs as well, then I'd say the gig is up.
2) The monetization story has changed. The humble indie bundle has shown that linux users will pay for games and play them on their linux boxes. Is this enough for Valve to change their stance since for the longest time they've said it didn't make economic sense?
3) Valve is working on a console and won't (can't) pay to license OSX/Win as the OS and is smart enough not to write one from scratch. This reason makes more sense to me. Getting steam client working on linux desktops is just a secondary benefit of their primary goal: getting the software stack for their console.