Top of this list used to be particular versions of Ubuntu
Summary: GNU/Linux "market share" in Steam grew by a quarter this past year, boosted by SteamOS perhaps, but watch the trends in distributions; even the Ubuntu-based distros aren't near the top (and SteamOS moved from Debian to Arch, so expect Ubuntu to stagnate further)
It doesn't look like Vista 11 will ever be adopted like prior versions and announcing a Vista 12 will mostly upset companies/organisations that only recently "upgraded" to 11