It's the environment, not the chipset, that's crucial.
Bruce is right - people shouldn't care what chip is in their machine, what they want is familiarity and all their stuff where they left it.
What Jobs is doing is making a radical change at the optimal time - Longhorn is still n years away, Linux isn't really maturing as a desktop OS - so now's the time to expend efforts creating a translation layer that will let OS X run on both big and little-endian systems.
The "Univeral Binary" that's being talked about - PPC and x86 binary in one 'app' (packaged directory tree, really) is fundamental along with Rosetta.
Support for PowerPC isn't going to somehow magically disappear as a result of this move to Intel, I think the endgame is to make OS X chipset agnostic.