I think that the day we see two editions of Mac OS X: PowerPC Edition and x86 Edition, is the day the same thing happens to MS Windows.
Therefore, we'll go from 2 major operating systems to 4:
-Before-
Mac OS X (for PPC)
Windows (for x86)
-After-
Mac OS X/PPC
Mac OS X/x86
Windows/x86
Windows/PPC
Therefore, we'll go from 2 major operating systems to 4:
-Before-
Mac OS X (for PPC)
Windows (for x86)
-After-
Mac OS X/PPC
Mac OS X/x86
Windows/x86
Windows/PPC