They are scheduled to begin the transition around June 2006, as long as they don't run into any major gotchas in the process of converting to Intel chips. I'd say they are probably waiting for the dual core Yonah Pentium M chips to become available. With those inside and running at 2GHz+, the Powerbooks would once again truly be powerful. The iBooks and Minis will likely wind up with the single core Celeron M version of Yonah. No one knows the exact date, but the current timetable is to have ALL the Mac lineup changed over to Intel by June 2007. Based on this info, coupled with Intel's published roadmaps which show the Yonah mobile chips launching in early 2006 followed by next gen desktop based parts toward the end of 2006, most people excpect the laptops will launch first next summer, followed by the Minis, and then Intel-based Powermacs and iMacs will arrive in 2007 once Intel has a non-Netbust desktop chip ready.
Once neat bit about the Yonahs is that are supposed to feature this new Vanderpool virtualization technology which will let a computer run two operating systems at full native speed at once (one core handling each OS in the dual core chips). This means that you may not only be able to install Windows on the new Macs, but you might even be able to run both OSes at the same time and be able to switch from one to the other like we switch apps now. Who knows how they will implement it, maybe OS X will be the primary OS with XP running in a window on the desktop with little speed degrataion besides the bottlenecks that are likely to occur from the two OSes trying access the same memory and stroage at the same time - but some of the newer tech like NCQ might migitate some of these slowdowns. It all looks to be quite cool, though.
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