OSx86 already runs on generic Intel hardware. There really isn't any technical reason that Apple couldn't use off the shelf parts for their systems.
But then they couldn't charge twice the price for similar hardware(and this is from a Mac user).
OS X runs via an emulation program, yes. No one's dual booting XP and OS X--at least, not that I know of. If they've progressed beyond an emulated install to full usage, please link me to some screenshots and "how we did this" pages. I'd love to be proven wrong on this.