I hope not...though if it does happen, Apple will be the first to do it. Vista only tried to catch up with Macs (doing it much crappier though) and didn't provide anything unheard of that no one would've guessed.
No...the parts aren't the absolute fastest, though the latest Mac OS (10.4) I've seen run very smoothly on a G3 (450MHz), and Mac OS's aren't resource hogs. (My eMac G4 at 1.25GHz with 256MiB of PC2700 RAM boots much faster than my other PC desktop with 1.8GHz and 1GB of PC4000 RAM) In short, you get much more out of the parts with a much, much better experience.