Will Linux end up being the primary OS for desktops and servers?

Servers yes, but Windows Server will still be a strong player. Server Core has improved this and features like AD, Exchange, branch cache and SQL Server will make sure most companies still run Windows Infrastructure.

Desktops no.

In the medium term I see desktop will split again in to 2 separate areas. The corporate workstation will continue running 20 year old LOB applications, becoming cheaper and more specialized. They will be more and more single replaceable units, and as IT centralizes it will be deployed and managed centrally. They will predominately run Windows, because those LOB applications were originally written for 16bit windows and at this point porting to a 64bit linux would be a nightmare. They are still largely going to be keyboard + mouse driven. A few business may end up going to linux, but this is likely under 10%

The consumer desktop will become more and more a "fixed" tablet or laptop. Touchscreen, novel and different concepts. Again largely as a single replaceable unit. These will run whatever the vendor is pushing and may be linux, but in the form of android or such.

Most consumers want whatever they're told to want.

More than anything, they're told what to want by marketing muscle, and they listen because they don't know any better.

Linux has no consumer marketing, or even consumer presence.