I've been thinking on why Apple came out with the Mac Mini and come up with 2 really good reasons why:
1. To have an entry level mac (at low end price) to go together with the iPod in bringing new userts to the Apple world.
2. To reduce demand for iMac G5 as the entry level mac and free up IBM's G5 supply chain to be able to make more G5s to be the heart of some new machine that is coming soon. (Apparently there is a ton of G4 processors available right now).

With that second reason in mind, is Apple coming out with G5 Powerbook soon? I've heard that it is still 6-12 months away because of power use and cooling issues with G5s as well as supply issues with IBM making enough G5s to keep up with demand - and I tend to agree with that guess-timate.

In my mind I've come up with a likely scenario and wanted to bounce it off some other Mac- heads to see if it sticks. Maybe I'm completely of the deep end, hopefully I'm not.

This is nothing but an educated guess, but here goes...

Last year, Apple introduced G4 iBooks, which actually pulled the mid-low end powerbook market into the iBook line. With the same processors as the powerbook and less than 15% processor speed difference, many students and others who were concerned more with price than a wide screen or power-user features now had no problem making up their mind to get an iBook over a powerbook. Although some people really were beginning to hold their breath because maybe this G$ iBook was signalling the introduction of a G5 Powerbook.

But the big announcement at MacWorld was the Mac Mini and iPod shuffle... not new powerbooks. A couple of weeks later, Apple quietly lowered prices on the G4 Powerbooks, which mostly got lost amid the news of iPods and Mac minis. But this price drop was setting off a mental alarm in my head because there was less than $500 price difference between the iBook and powerbook line. Something just felt wrong - like Apple was trying to get rid of the 12" Powerbook. Why would they do this? Is this another sign of G5 powerbooks release coming soon?

After a few weeks though on this, I am leaning towards Apple introducing a new Powerbook at WWDC this spring, however, it will not sport the G5 processors that everyone has been waiting for. It will be a major redesign for a new G4 powerbook which includes dual-processor options ( Yes, twin G4 processors in a powerbook).

These "G4.5" powerbooks would still keep the 15" and 17" widescreens, but the smallest Powerbook would now have a widescreen as well (not sure of size - 10.6" to 13.3" range). The small one would be about $1600 for a single processor and $2100 for dual processors. Add roughly $500 and $1000 to those prices respectively for 15" and 17" models. The secondary processor would be idle when running on battery to extend battry life. There would obviously be other improved features as well, including a semi-redesigned case that would extend the life-cycle of the current Powerbook line out another 9-12 months..

My reasoning: (if you've been patient enough to read this far)
Apple and IBM really seem to be concentrating on sheer processing power and speed for the G5s right now - they are focusing on winning the battle over consumers' (and enterprise's) perceptions and mindshare that Apple really is the best. Not just in performance, but in specs too. We all know that Apple computers match PCs on performance any day of the week and we (most mac users) don't really care about having more MegaHertz. But a lot of people do and Apple needs to win them too, just like they did with the iPods.

If you think about it, we are just getting there. Just ask PC Gamers what the hottest gaming processor is and they will tell you the AMD Athlon FX55. That processor is 2.6GHz running at 64-bits with 1 MB of cache. The dual processor PowerMac is more than a match for that.

I don't think a G5 Powerbook plays well into that goal for perceptions and mindshare in the short-term. A G5 Powerbook right now would only be about 1.4GHz in order to keep power use and heat down. A notebook of 1.4 Ghz just doesn't sound like it is ahead of the pack. The dual processor option would give power users some real muscle and really take pressure off to hurry out a G5 Powerbook. It would also give Apple that "World's only..." tagline they love throwing out there - "The World's only dual-processor notebook"

This would also allow Apple and IBM to give the technology another year to get the cooling/power consumption/supply chain issues worked out and really come out with something special enough to meet people's expectations of a truly innovative Apple design.
There is certainly no end to the availability of G4 processors at a fair and reasonable price to keep up with the demand for Mac Minis, iBooks and even Dual-proceesor Powerbooks . So, over the course of the next year, I would expect G5 Powermac desktops to get bumped close to 4 Ghz and G4 iMacs to be just under 3GHz, while Apple waits to unleash a 2.5 GHz G5 Powerbook in mid '06.