Forget G5s in portables - at least until next year. That was just a completely unfounded rumour from the most notorious Mac world "entrepreneur" Jack Campbell on his totally bogus web site, MacWhispers.
The new 15" will be interpolated between the 12 and 17" machines which are real beauties. I'd expect a speed bump to 1.2 or 1.33 GHz since the current 15" machine is at 1 GHz. Or a price drop.
The 15" will just be a more affordable 17" (which Apple got sooooo right except for pricing out of many peoples range).
It's just a dream to use. I hooked up my 22" Cinema display to it to generate 2.9 million pixels of Quartz Extreme accelerated real estate. I get whiplash...... Oh, and during the initial phase of the power outage, seeing the keyboard instantenously light up as the lights died and the AC was interrupted almost made it poetic (although I did have to shut down a few hours later).