I think it's coming very soon, perhaps in the next generation of Macbook Pros. The writing was on the wall when Apple released the new iPad Pros: https://bgr.com/2018/11/01/new-ipad-pros-speed-will-be-a-nig...

I know these are synthetic benchmarks, but it's incredible to see the A12X outperform the iMac 27" Retina... These chips have the potential to blow the doors off of Intel's Core i7/i9 while having 2x the battery life.