I'd give this a less than zero chance. I'm not sure how else to say this.
Being Mac exclusive would mean that whatever studio would make the game is deliberately skipping out on 90% of the desktop market. For a AAA game, that's just not financially feasible.
Let's be realistic, if Apple shows off gaming at all, it will likely be a demanding title that's been ported to ASi, sans benchmarks. Or it will be playing iOS games on the Mac at full res or something.
Nah, Nintendo Switch works that way.