Apple has released a project to run Windows XP on the new Intel based Macs. This’ll probably be just about as successful as the IBM strategy to run Windows 3.1 applications natively on the OS/2 Desktop; just when they got it working, Microsoft released a new version of their operating system (Windows 95) and no one wanted to run Win 3.1 apps anymore, so everyone gave up on OS/2.
Fortunately OS X is much better than OS/2, so I doubt that Vista will make many of the Mac faithful run to install it on their Mac even if Apple supports it.