Folks,
I'm starting to think that Apple's going solidly toward a 3-product matrix across all product lines:
Desktops:
Mac mini, iMac, Mac Pro
Notebooks:
MacBook, MacBook Air, MacBook Pro
Tablets:
iPad mini, iPad Air, iPad Pro
Phones:
4-inch model (coming soon), iPhone 6, iPhone 6 Plus
Watches:
They may do this here, too.
So I'm expecting the differentiator between the MacBook, MacBook Air, and MacBook Pro to be chipsets. The 12-inch MacBook will utilize the Skylake m3 processor, the 13- or 14-inch MacBook Air will gain retina along with new keyboard and trackpad and use the Core i5/i7 ultra low voltage model, and finally the MacBook Pro will use the Skylake quad-core i7s. Now they'll all have Thunderbolt 3/USB C ports.
As you'll note with the desktop, each type of desktop uses a different chipset (Mac mini with dual-Core i5 processors found in 13-inch MacBook Pros, iMac with desktop quad-core i5s, Mac Pros with Xeons). And starting with the iPads, they're differentiating size by processor (A8 for the mini, A8X for the Air, A9X for the Pro).
The extent of any re-design could range from minor to major. The MacBook Air has the most to gain in the re-design department. When Apple added Thunderbolt to the MacBook Pro they didn't re-design the computer. However, with Apple's new battery terracing design, and the new butterfly keyboard and force touch trackpad, they will probably re-design the computer to accommodate the MacBook's new wider, larger trackpad style. They probably didn't do it with the last revisions because of the logic board and battery designs that were already in place.
I'm wondering if Apple will ditch the 13-inch MacBook Pro with optical next go around, and surprisingly, also kill off the 13-inch MacBook Pro with retina. My rationale for this is the difference between a 13- or 14-inch retina style MacBook Air will be blurred compared to a 13-inch MacBook Pro. The only way I think Apple keeps the 13-inch MacBook Pro with retina around is if it adds quad core processors to it.
I'm thinking Apple's aiming for clean, concise product lines and 2016 and Skylake will finally let them accomplish that.