Apple is on track to diverge from ARM and x86 to design its own proprietary instruction set. This good for the future of hardware–software co-design.
With all of Apple’s vertical integration efforts (own ALL THE THINGS) it certainly seems likely that they’ll want to bring this last piece in-house as well. The linked article astutely recognizes that small steps towards this have been made with the Apple Watch—apps are no longer delivered in bytecode, but instead in LLVM IR, which paves the way for their future proprietary ISA.
Source: The Apple ISA