I'd say the year of the Linux desktop has aalready come, twice.
On one weekend in 2007, over two million *nix desktops were booted for the first time. It just so happened that *nix was BSD based, and had an Apple GUI. The year of the "Linux" desktop was the year of OSX. Not the kernel we hoped for, but a mainstream POSIX system that will run all your GPL code.
Then in 2010, millions of new systems had the Linux kernel. Today, MOST new computers have Linux installed. By 2010, the ubiquitous consumer PC had shrunk to fit in your hand. All of these lovely Linux systems had a nice GUI from Google. Since most new computers are portable, not chained to the desktop, I don't know if any future year of the Linux DESKTOP matters too much.