Valve going into hardware is definitely one use of Linux support, however another is as an alternative to Windows 8 and OS X. Both Windows and OS X are moving towards an locked-down, app-store model and Gabe Newell recently expressed concern over that move. At the same time, Ubuntu is being sold pre-installed on computers worldwide (though less so in the US and UK, more in emerging markets). I'm not saying that Ubuntu will reach OS X's current level for Steam users straight away, but in 5 years or so, it's definitely possibly.
Yeah, I would rather believe that way of thinking. Who knows what Apple and Microsoft may do next to lock down their systems further, and extract more "tax" out of everyone publishing applications or games? The only way for a company like Valve to prevent a direct attack on their revenues is to develop a solution for an open system. It may very well be that it is not necessary in the end, but they are just planning for future scenarios like any other respectable company.
They are however Canonical is not moving towards locking down the OS which Apple and Microsoft are doing (though fans of either won't admit it). That's what Gabe is scared of.
