Hmm, because in my experience (which admittedly isn't vast with the power PC architecture yet) there's several things different about being on the powerPC side of the fence:

1) Apple people in general tend to hold on to equipment a lot longer before being forced to upgrade
2) each release of the operating system runs *faster* on the old hardware than the previous release, not slower (this in itself contributes greatly to (1) above). This didn't apply when they jettisoned system 9 for the new OS X of course, but has generally held true otherwise.
3) just because there are "hooks" for fat binaries doesn't mean everyone is going to distribute them.
4) in general that means I suspect that yes, I'd have to buy a new machine in 3 years. I am used to buying PC's every 3 years, I wasn't planning on upgrading my mac that quickly. I'm sure as hell not going to fork out $3k for a machine that I'll be forced to replace in 3 years because the newest stuff doesn't run on it (and no, I sure as hell don't blow $1k per year on intel hardware either, I'm a miserly sob). I know as a pc user I just sucked it up when I had to buy new hardware constantly just to stay "supported" but I really wanted to get off that rollercoaster.

-- Gary F.