Both IBM and Motorola compete in the embedded market with PowerPC processors, I personally think IBM is very far ahead of Motorola in that market which is why Motorola has been trying to sell their microprocessor division for quite some time now. Further, IBM uses their own chips in both workstations and servers. There R&D for the past 5 years with the PowerPC architecture has been completely Apple independent.
Apple never used a POWER3 processor in any of their systems. Apple never used a POWER3-II processor in any of their systems. Apple never used a POWER4 processor in any of their systems. Apple never used a PowerPC 405/440 processor in any of their systems. Apple stop buying PowerPC 604e processors from IBM back in 1997, yet IBM still makes them and systems that use them.
No one wants to lose a customer. But Apple hasn't been providing IBM all that much business in the last 5 years. And IBM just kept on innovating (the real thing and not Microsoft's buzz word). Apple threw more business at Motorola then they could handle at times (at one point IBM made G4s for Apple when Motorola couldn't make enough), and yet they had a hard time doing anything new with their processor line.
It would be in bad taste for Apple to threaten IBM. And I'm not sure IBM would care all that much anyways as they have their own goals with this technology and Apple has been out of the picture before. Motorola is the company hurting in this area, not IBM. Both Apple and IBM are going to continue on with the PowerPC architecture, Motorola is the company which may soon be out of the picture.
In all reality, the PowerPC architecture is IBM's child, not Apple's and not Motorola's. When Apple was designing the 61/71/8100 series computers, Apple left open which processor they planned on using, Motorola's 68060 or IBM's PowerPC 601. In the end, Motorola couldn't get their processor into production in time (not much of a surprise for those of us who have watch Motorola over the years). Part of the reason for even getting Motorola involved in PowerPC at all was so that it didn't look like Apple was moving to IBM (the pre-Microsoft villain).
And Apple's work on an operating system for Intel hardware has not been a secret (Rhapsody/Darwin) and wasn't a surprise to anyone who could have saw it as a "shot over the bow".
Apple was not threatening IBM, in fact Apple should have dumped Motorola as soon as they had problems making G4s faster than 500 MHz (and IBM was able to produce 600+ MHz G4s at the same time).
It shouldn't be under estimated how important IBM is to the PowerPC architecture. And by the same token, we shouldn't over estimate the importance of Motorola (who maybe out of the picture soon than you would think).