I disagree from a bit of an odd perspective. Apple does do this when it comes to their Pro lineup recently. iPad PRO (distinct change from curved), Mac Pro (distinct change from can). In fact, their most recent change to a Pro device was a complete 180 (back to the tower link form factor).
My hypothesis remains that the Pro will evolve into something very different than the MB or MBA... it will be quite more expensive, possibly modular, and perhaps a reboot towards the true Pro ideals.
You're talking design change, which could most definitely happen. But Apple isn't going to make a thicker laptop with all of the ports that the previous models had. It would be admitting to a mistake, and that does not happen. The likeliness of them doing that is about as likely as them adding a headphone jack back to their phones.