JIT translation has come a long way and MS plans to do exactly this with x86 software runnning on ARM in the near future. It’s not impossible that A12s with custom silicon working in concert with software JITing could provide a decent experience.

I would be a lot of work though. You don’t just have to translate the compiled user apps, you need to make things like AirPlay work, and that's an example of a feature that uses specific hardware acceleration. And some things like Thunderbolt might not work at all without Intel’s help.

They don’t sell hundreds of millions of macs. It might not be worth it. Why not just wait a year? It’s not like Windows laptops have access to better chips than they do.