The Steam Hardware Survey covering March 2014 shows the Linux usage coming in at 1.20%, or a drop of 0.10%. As said in past months though, this is basically flat-lined and has been for months. When factoring in a margin of error and other factors, there isn't much change with the Steam Linux numbers usually come in at just over 1%.
I wouldn't anticipate any major changes in the Steam Linux gaming market-share until the roll-out of the Steam Machines, SteamOS becoming more stabilized, and more AAA game titles being available on Linux.
Those wanting to see the latest Steam Linux numbers can visit the Steam Hardware Survey. You can see coverage from previous months via our older articles, but in general there's been no major changes as of late without a compelling reason for Windows gamers to migrate to Linux, no major Linux game exclusives, SteamOS still being in beta, the Linux graphics drivers still maturing, etc.