Linux will rise in popularity, but not as a Desktop OS
The great things about Linux is it's small, scalable and free. These strengths lend it to specific application rather than general use. For instance, Linux could be used to run sophisticated vending machines with credit card processing, engine management for automobiles, internet servers, etc.
What happens to Linux when you try to make it a desktop OS? You get bloat. The Linux kernel is becoming more Windows-like, by necessity, the more it tries to gain the desktop market. In the mean time, Windows is trying to slim down and challenge Linux in the scalable arena. Server 2008 can run without the GUI in a command line mode that keeps its footprint small - perfect for a print server, network management or other specific task-oriented roles that Linux currently excels at.
I'm not saying Linux can't compete with Windows on the desktop, only that to compete it must so drastically change that it becomes something different than it was. Linux has a wide open market available to it, its just not the desktop market.
