Apple is the company that just over 10 years ago made a strategic move to remove Intel from their supply chain by purchasing a semiconductor firm and licensing ARM. Managing 'painful' transitions is a core competency of theirs.
The new Apple–ARM work would eventually evolve into the ARM6, first released in early 1992. Apple used the ARM6-based ARM610 as the basis for their Apple Newton PDA.
68K -> PowerPC, practically seamless
Mac OS 9 -> BSD / OS X with excellent backward compatibility
PowerPC -> x86
x86 -> ARM
Each major transition, biting off orders of magnitude more complexity of integration. Looking at this continuum, the next logical vertical integration step for Apple is fabrication. The only question in my mind, does Tim have the guts to take that risk.