If you stop and think about it this makes sense. Apple has always wanted to manufacture its own chipsets in house and they are annoyed with Intel (for their own reasons) and have been looking around for a replacement. We can safely rule out AMD as they are not making anything to support Intel and probably won’t for the foreseeable future. This leaves nVidia, but Apple would not have sufficient demand to make buying the chipsets from nVidia worth either company’s time.