One of the reasons Apple is switching to Intel is that the chips are cheaper. Yes, they have faster clockspeeds than the G4/G5, they run cooler, but they are also less expensive. This should allow Apple to actually cut prices, although they may take the higher margins for awhile.
If you look at Apple's current line-up, the flat-panel iMac, with a nice G5 chip, and 17" screen is $1300. That's not exactly out of line all things considered. I don't see Apple actually raising prices when they start shipping Intel powered Macs, although it will be a bit surreal to see "Intel Inside" on a Mac. :lol