I don't think this will be the case at all. Apple isn't going to let you run their OS on PCs. A huge part of their revenue is from hardware
Yur right... Apple will try to control their platform/OS and work on specific hardware too.
Sure, people will manage to get it on PCs and there will be hacks etc... but I doubt it will be anything big. Plus OS X isn't Open Source so there's less incentive for the OS community to bother with it.
Actually MacOSX is open source. See darwinsource/. I knew that they are based on BSD Unix, but just realised they are open source too!!.
IMHO the OSX hacks will get quite popular if it happens..