Is the Freescale 7448 pin-compatible with the latest 7447 Apple uses in the PowerBook and/or iBook? If it isn't, then Apple would have to do engineering work on a design that "might" have 6-9 months of life - kinda expensive.
I don't see Apple using existing Intel CPUs, such as the Celeron or Pentium Ms for mobile & consumer, or the Pentium D for PowerMacs, which leaves the new chips - remember, Apple was looking ahead at Intel's roadmap. And I don't see the iBook getting Yonah before (or unless) the PowerBook does. The first version is the 32bit, dual-core version dubbed Centrino Duo. It has a 667MHz frontside bus and 2MB of L2 cache, as well as the other bells & whistles of the Napa platform.
Therefore, it makes no sense for Apple to put that dual-core speed demon in the iBook - even if they left it with the Intel integrated graphics, while hobbling the PowerBook with either the present 7447 G4, or, even, the dual-core 7448 (which, if I recall, has a 200MHz fsb).
No, I think it will be PowerBooks "announced" on January 10th, for availability around the first week of February. I believe the iBook may take over some of the present PowerBooks "hi-end" features, but otherwise wait until (around) May, when Intel releases the single-core Yonah, dubbed Centrino Solo(?). If... "IF"... Apple switches the iBook to Intel at MWSF it only makes sense if there's still a "respectable" performance gap between the PowerBook and iBook (lower-performance & clock speed of Yonah, even if both are dual-core; FrWr 800 vs. FrWr 400; Pci-Exp. x16 GPU vs. Intel integrated graphics; S-ATA hd vs. ATA-100 hd; etc.).
And if you feel you need to wait, buying a G4 PowerBook now, consider this: Next after Yonah comes Merom (September-ish). This beast will be a 64bit, dual-core cpu (I think the iMac will wait for this cpu, too, because it's a "sticky" marketing point to drop back from 64bit G5 to 32bit Yonah, even if latter is dual-core). And, for my 2 cents worth, I think that both the iBook and PowerBook lines will split into 4, more-rounded, product offerings:
• iBook "Jr.": 12-13" WS, Yonah single-core, Intel graphics, Centrino 802.11g, etc.
• iBook: 13-15" WS, Yonah dual core mid-perf., 64MB PCI-Exp x16 low-end gpu, Centrino 802.11g, etc.
• PowerBook: 13-15" WS, Yonah dual-core hi-perf., 128MB PCI-Exp x16 mid-range gpu, Centrino 802.11g, etc.
• PowerBook Pro: 15-17" WS HD, Merom dual-core hi-perf., 256-512MB PCI-Exp x16 hi-end gpu, Centrino 802.11n, etc.
Bottomline: I've been limping along on my G3/400 Pismo the past 2 years - it killed 2 DVD-ROM drives in the first 3 months, and the 3rd one died in 2004. I've considered getting the iMac G5, especially after the recent upgrade. But if Apple delivered a Yonah PowerBook in January I'd snap one up. Much of the "Rosseta lag" would be eased (not erased) by the higher clock/bus/gpu speeds. Also, Apple's had MacOS X on Intel since it was in beta. You know they've had "Test Mules" running it on most variants of Intels mobile, desktop and server CPUs in their deepest labs during that time.
Steve's announcement at WWDC this past June wasn't on impulse - it had been "in the works" since Rhapsody. And Logic, now part of Apple's stable, will be one of the first "pro apps" optimized for x86... In fact, by WWDC '06 I predict that all of Apple's Pro apps will be running smoothly on x86. In fact, I wouldn't be surprised to see Adobe CS3, Maya, MS Office and other big names all x86-ed before MWSF '07... Alongside Merom comes Conroe for the PowerMac and Woodcrest for the XServe.