IMO the one thing that could kill Windows would be if Apple released OS X on other platforms. I do plan on buying a Mac, however it may end up being a couple of years, but if OS X was released for all Intel computers then I'd definitely download a copy and have it in dual-boot, which could take me away from windows long enough until I got a Mac. Or even then I'd consider buying a Linux version from Dell and install OS X (it'd probably still be cheaper than going with pre-install windows).
Making OS X support that much hardware is just as hard as Linux supporting that much hardware, only with significantly fewer engineers available to do the task.
My Dell laptop has identical components to most MacBooks, so I'd say 90% of the drivers OS X already supports would be involved in my Laptop.
It doesn't necessarily have to support every variant. I just mean it would be amazing if Apple struck a deal with Dell so that OS X could run on their laptops. However, I think Apples decision to support outside hardware will likely be an image thing over a cash thing. If Apple compromises its image then it could potentially compromise their entire business.
