They will have to work really hard
Perhaps at the beginning with all the hype around the iPod creti and pleti is curious to see a Mac. So Apple will certainly profit from the change.
But using the same chip as the other mass marketers do, will be of no advantage, if the OS is not ways superior or favourable for other reasons. This is something one experiences with SGI, which is more and more fading away into oblivion.
Further, Apple might see itself in the well-known position, that the AMD chip will be superior performance wise, or performance per Watt wise or both and they stick again to the "wrong chip". But this time this is more dangerous, because one has the real comparison.
Also, after reading the specs concerning the new dual core machines for Computer Graphics applications it seemed to me, that the G5 is great, but Apple exactly missed out on the software, i.e., on the drivers for the graphic cards.
That is not a good sign for the pro market. Why should a pro buy an x86 machine from Apple, under such conditions.
Also, probably IBM will (has) to put out in a second iteration mature Cell
type processors that really mean a jump ahead.
All in all, in the long run, it does not make sense for Apple to give up the
PowerPC side, at least not for the pro environment. If not, they will end up being a consumer product company.