I don't know, all my close friends and family are running Linux as their main OS. You might just wake up one day to realize that Linux on the desktop has already happened.
Edit: I stand corrected.
* They try (and arguably succeed at) cloning Unix.
* The adopt a permissive license for sharing and copying.
Beyond this, they're 2 completely different projects with nothing more in common. Heck, even the "permissive licenses" they each use are contradicting in philosophy.
You seem to imply that Linux has reached ubiquity on the desktop because MacOSX is based on BSD. This is just wrong.
> * They try (and arguably succeed at) cloning Unix.
No, the BSDs actually are Unix, in a genetic sense.