That'll most likely never come to pass.
Apple knows that's a big concern for a lot of its customers, who will just migrate to Windows, cry a few tears, spend 3 to 4 weeks adjusting to the equivalent software on that platform and then never look back.
I know I would. It's literally 5 minutes to get on dell.com, order the latest XPS 15, which is a glorious laptop, and wave Apple on its merry way.
Such a move would sound the death knell on the Mac platform. I'm certain that Apple
has tested the concept with focus groups, developers and select software partners behind closed doors, so they know the calamity this would cause.