The recent OSX update 10.3.4 reveals that new PowerMac or iMac G5 are existing, ready or close to be launched.
The previous update already included an unknown reference code: Power Mac 7,3.
None of the current Apple computers owns such a reference code. Indeed, reference code of the current PowerMac G5 is Power Mac 7,2.
For information, PowerMac G4 had as reference code Power Mac 3,x, Cube G4: Power Mac 5,1 and iMac TFT and eMac Power Mac 4,x and 6,x respectively. You can find the complete list here:
http://www.theapplemuseum.com/index.php?id=tam&page=products&subpage=newworld
Now if we look in details in the last MacOSX update, we can identify a new reference code: Power Mac 8,1, so it would mean that it is not an update of one of the current model, but a brand new model!!
We can also find the reference code SMU_Neo2, which could mean that Neo2 would be a new version of the current processor. If it is clear that the new processor will be derived from the current one, it is not clear if it will be a light version (such as the 970fx in the Xserve) or a boosted version (!!!)!
If you want to know more, look inside the last update 10.3.4, open this file:
/System/Library/Extensions/AppleMacRISC4PE.kext/
Contents/info.plist
and search for "8,1".
Knowing that the PowerMac G5 and the iMac have not been updated recently since a long time, then you can conclude...what you want... ;-)
I let you dream...
(for me, my personal feeling, the PowerMac 8,1 is an iMac G5 with a new design, available at the end of June, whereas the PowerMac 7,3 will be the revision of the current PowerMac G5, available at the same time)