This is probably the official end of a long relationship between Apple and Nvidia. Originally Apple liked and often used Nvidia chips as graphics accelerators in their Macs. But after disputes about defective hardware in MacBooks, the relationship between the two companies had been strained for quite some time. For example 
Apple was hesitant to sign new Nvidia drivers recently in its OS updates and for years has only relied exclusively on AMD as GPU supplier for its macOS devices.
After Nvidia still seemed to be trying to provide Apple users with the latest drivers, now it's time to stop using good refills. Nvidia has officially announced that it will not develop new CUDA versions for macOS any more.
This step is more than understandable. After all, there is no Apple hardware available for years that contains NVidia chips. However, from the end of this year there would be with the new Mac Pro after years again a computer, which could potentially accept Nvidia hardware via its PCIe slots.
And indeed, there are even some potential buyers who have considered such a combination. Because in the emerging area of machine learning workstations there is currently no way around Nvidia and Apple's upcoming Mac Pro has been an interesting basis for users who wanted to drive Tensor Flow and its rivals with a lot of CUDA performance until the current Nvidia decision. From this point of view, Nvidia's last counter counter for Apple might still be a bit painful.
CUDA also plays an important role in the video sector, but the industry has recently been equipped with alternatives such as OpenCL or Metal. RED in particular is still completely dependent on CUDA at the MAC, but has already announced that it wants to rely on metal in the future. And on the PC CUDA will be maintained and cared for anyway.
For Nvidia this decision might have less effects than for Apple. Users will have less choice on the Mac in the future (also via Thunderbolt 3) and developers who develop for both Mac and PC will possibly save themselves a parallel CUDA development in the future...
