I've owned Macs since the Mac Plus in 1986. I've seen a number of these kinds of transitions, and frankly I fail to see why Apple should feel obligated, at this late date, to support such a legacy platform. While Apple may not stay with x86 forever, I sure don't see it going back to what we presently know as the good 'ole PPC platform. In my estimation, by the next time Apple makes some kind of CPU platform transition, everything they've ever supported prior to x86 will by then be nothing more than a distant memory.
If anything, Apple should practice good open-ended coding techniques and stay abreast of all the as-of-today high-end CPUs and CPU developments. However, what Apple needs to focus on is doing one thing and doing it very well. You can't have that happen (at least as easily) with divided attention and divided loyalties.
Hopefully, sometime in the next few months I'll be the proud owner of a brand new MacBook. I'll be very happy to have transitioned fully to x86. My main system at the moment is an Ubuntu 8.10/WinVista dual-boot PC, since I just can't deal with using this 1.5GHz Mac mini for multimedia and even modern web browsing tasks. The jump in performance between a 1.5GHz G4 and a 2.4GHz Athlon couldn't be more amazing to me.
RISC had its time in the sun. In certain respects, it may be technically better or more efficient, but Intel's x86 32 bit and 64 bit systems have simply beaten it out in sheer horsepower. In my mind, this argument is long-since over.