That's not exactly true ... Apple put the physical controls back on the iPod Shuffle after the 3rd generation which removed them completely. But the bigger back-step was Firewire on the Unibody MacBook. They removed the Firewire port on the first aluminum unibody MacBook, which replaced the original white MacBook, but then returned it to the upgraded 13" MacBook Pro, and reintroduced the plastic unibody MacBook with the Firewire port.
So it's rare, but it happens. My guess is if Apple did this, they would try to save face somehow by adding the port back to the Plus model since it should have sufficient room to accommodate it, or they will offer a separate SKU which has it, but in limited color and RAM and storage choices.