I think we will be looking at a generation of emulators that can transparently access the CPU, like Virtual PC does on the x86 systems and boot (hopefully) MacOS natively.
the "ring 0 sharing" approach is the only right one if there is no way to do a multiboot on non-apple x86
as maconlinux or colinux r doing right now
they r transparent layers between the guest os and the host one but no hardware is emulated and it's all natively run
guest os cannot touch the hardware directly
but hardware calls is intercepted by the layer and then putted on the "queue" of hardware requests
virtual pc or vmware are virtual machines that totally emulate the x86 architecture, hardware etc
so it's very heavy
The switch would probably cause PearPC to slow down a little, but it will remain, and join the "club" of SheepShaver and Basilisk II, serving as an emulator for an older machinve. Besides, there will still be Linux/PPC.