Potentially keeping AMD as a partner is graphics on the high end is a good point- i.e. iMac Pro/Mac Pro. But since its 99% likely that all the other Mac's will

Potentially keeping AMD as a partner is graphics on the high end is a good point- i.e. iMac Pro/Mac Pro. But since its 99% likely that all the other Mac's will be SoC with no Windows driver support for any of the underlying silicon, I'd find it very surprising if Apple went to the trouble just for the high end. That said, I thing Intel Mac Pros will be a thing for a long while, even is a 256 core ARM variation came out, just to keep the pros happy until they can comfortably transition to the new stack. Apple has spent too much human capital recently on the pro team to make me think otherwise.