On the desktop: For Unix based oses in general the goal should be to reach 20% or more market share. Windows will remain king here for some time but it lacks innovation and in general Microsoft keeps releasing Windows Vista. Desktops are becoming much more of consumer devices and Linux/Unix is better suited for that in my view, the Arm powered Chromebook is evidence of it.
On Mobiles: While Unix dominates here much of it is controlled by closed oses. A goal would be to have an OS like Ubuntu Touch, Sailfish, or Tizen offer a 3rd platform and take the place currently held by Windows Phone and 4th platform currently held by Blackberry.
On Servers: Windows still has a market share of about 30-40% reducing it down to 10-20% is a worthy goal.
Game consoles: Ever since the loss of the GP2x there aren't many options for open game consoles. Game consoles remain closed hopefully Android gains some market share on home consoles with devices like Ouya and gain mobile market share with devices like the Archos gamepad or those various Chinese Android handhelds. Consoles are an area that remain stagnant and need competition.
In my view with right efforts these goals are doable and the opportunity is available.