Zero. They can't sell any upgrades which would put the cMP in front of the nMP. They just stopped to care about this business, the rMPB with it's tiny entry-level GPU is the new FCPX workstation. It's enough for fancy YouTube clips and the real work is done on other hardware now.
What about Mac Edition cards for TB3 enclosures, which the new MBP's and supposedly refreshed iMacs and Mac Pro's will surely benefit from?
Apple could release a TB3 GPU enclosure akin to Alienware or Razer in a much better Apple-eque design? Maybe, incorporate a few more practical benefits of adding dock-like functionality?
Mac Edition Polaris or Vega GPU's would make sense in that sense addressing past customers and present and future customers, at the same time.
Everyone wins. Everyone is happy. Everyone is making $$$$
1. Apple design team gets to design a TB3 enclosure.
2. Third-party GPU vendors (including AMD themselves) are happy that 1% of the market has suddenly opened up for them.
3. And, we, the users are happy about new Macs being "upgradeable" again.
4. No more octopus/dongle syndrome of wires all hanging out from Macs with this supposed TB3 enclosure that is also part Docking Station.
5. Multi-GPU opens up gaming potential for new rMBP owners and future Mac owners with TB3.
6. Multi-GPU opens up video/audio/animation/CAD productivity users with more access to GPU compute units for better, smoother, faster productivity
7. Used Mac retailers/sellers are happy that the value of at least mid-2010 and 2012 Mac Pro's have suddenly risen due to this prospect of elongating its value from new Mac Edition Polaris/Vega GPU's
8. The Earth is happy that these old Mac Pros are not being put in landfills for recycling as well as the new Polaris architecture being more power efficient. Thus, lowering carbon footprint
9. Hackintosh community is happy because they can now buy cheaper PC variants and have a kick-ass hackintosh
10. Current ppl with RX 480's (or 470's/460's) in their Macs can flash them and get full ROP usage with their cards now... also enable correct PCI System Report and About This Mac ID....