Apple is typically cryptic in its response on the issue of whether Intel-based Macs can run OS X: the official line is that “Apple has no plans to sell or support Windows”. But notably, this answer doesn’t rule out running Windows on a Mac. Indeed, Apple’s vice president of Worldwide marketing, Phil Schiller, said as much following Steve Jobs’ keynote announcing the Intel Macs. “That doesn’t preclude someone from running it on a Mac. They probably will.”

Whether Intel-based Macs can run OS X

Now, it still keeps mysterious. However, I guess the ultimate answer is "Yes". Let's wait and see. By the way, is this another great ambition that lies behind Steve Jobs's motive to adopt Intel CPU to Mac?
If Mac can run Vista plus OS X but PC can't run OS X, which computer will you buy? In this way, is there any possibility to increase the prevalence of OS X & Mac?