There’s no danger of Apple dropping nVidia graphics, especially the discrete graphics. What’s at issue here is the nVidia chipsets. Intel is claiming that nVidia doesn’t have the right to produce chipsets compatible with its newest line of CPUs, something nVidia disputes.
In a nutshell, Intel is running scared because of technologies like OpenCL that threaten to make the CPU less dominant in the overall architecture of personal computers. GPU technology has evolved at a much more rapid pace than that of CPUs, and APIs like OpenCL are trying to take advantage of the extra horsepower. As one of nVidia’s co-founders recently put it, what’s really happening here is a battle for the soul of the PC.