I don't consider these reports strong evidence, but I DO think it's LIKELY to be soon (announced at least, maybe not shipping right away).
And the evidence for it NOT being soon seems much weaker.
But which model(s) will be first? Could be any of the three G4 lines--but I think the other G4 Macs will follow within a month or two, so I'll try not to be TOO disappointed if the PowerBook I want doesn't show up January 10.
And I think some of the current G4 models will be STILL be sold, alongside the new ones, so people can choose what they want--based on how long-term their needs are, and what apps they demand top speed from. (I use Photoshop all the time, but not for huge images--so I don't demand top speed from it. And I want the next generation platform, so I'm willing to settle for months of Rosetta for some things.)
Apple has sold the old model alongside the new one several times since Jobs' return, and it would help ease this transition just like it has in the past (OS 9 to X, G4 to G5, etc.).