Very true, but with the likes of the Asus Eee PC being released with Linux, and it's competitive price. The flood gates may open soon.
It's human nature to stick with what feels comfortable, and since MS has pumped the market full of their OS for years, it will take time for the masses to accept change.
But with the current financial situation, people will start looking for a bargain, and Linux is certainly that. I see open source as the future, as long as people are informed and educated that they have a choice.
When Linux becomes idiot proof (I.E. does away with the need to understand Terminal) then it will be the death knoll of MS.