selfish or not ... please note i stated: as a slave. you certainly know there is a basic difference how PPC and x86/x64 processors and operating systems handle data (big vs. little endian, different calculation units, ect)
since a long time no PPC computers are produced, so we can't expect them to become more or more powerful - PPC are often not even powerful enough for Vienna Instruments only, they are definately not powerful enough for the Vienna Suite convolution reverb.
forget G4s completely ... you can use them for browsing, emailing and your homework, possibly some very basic and low level musical work (in the sence of performance requirements).
you could still use a G5 as master (many PT users are so to speak locked to this platform) and PPC plugins.
XP, VISTA, Windows7 (and to some extent even windows 2000) does not require different development, only for AMD processors a few additions have to be made ... so nothing needed to be doubled here.
sorry, but we have to face reality - would apple have decided to continue producing computers with the G6 processors it would be another story.
christian