Apple will still be selling and supporting x86 machines for many years, possibly forever.
On the portable side though its a no-brainer. I don't see Apple having x86 in new laptops at all after the transition.
But Apple may stop making high end desktop systems all together so it is possible. It's a very small part of their revenue.
That's what they said when the Mac Pro was neglected and they still designed a brand new machine to sell.