I doubt there will be any major repercussions at all. Even if it manages to bring game developers back on the Mac OS side, you have to question Apple's LATE response to the market. What they revealed yesterday at the Keynote was something they should have jumped on about 1 or 2 years ago.
Palmer was right and so were the others regarding Apple's lack of GPU power to handle VR. Of course, when it comes to gaming, I think most people will go with PC or game consoles as they're much cheaper.
Think about it. Do you realize how expensive it is to buy an iMac or Macbook Pro and buying an external GPU as well for gaming? These machines were built for lack of upgradability except for RAM. For VR development, the external kits would be handy. But for a consumer? It would be crazy expensive. Customers, I suspect, are better off having a modular PC or Mac to be able to upgrade for gaming as time goes buy.
The iMac Pro, so far, has the specs to do it but the chassis design doesn't seem to be right for that. And it's $4,999 for starters which is insane. I'm sure anyone who does development would jump on that machine which may not be completely upgradable as the next Mac Pro which is supposedly modular in design ( something that should've been done a LONG time ago ).
Some of the new iMacs with Kaby Lake chips are questionable. Having an external GPU is a good idea for starters but should've been done earlier.
Apple has a LOT of catching up to do.