I think the chip says Apple all over it. It's better performing than the G4, offers good memory bandwith, and has an Altivec compatible vector unit. It sounds perfect for Apple. And it could be in Macs in the second half of 2003.
I can also see IBM moving it to a .9 micron manufacturing process to speed it up later in last half of 2003 or early 2004.
Here's an interesting, if mostly speculative, letter to MacinTouch regarding IBM's new processor in comparison to other processors (both shipping, imagined or otherwise). It also highlights all the "ifs" involved in this scenario.