Apple has beaten all other ARM SOC designers to an ARMv8 core and that too by atleast 9 -12 months. The decision to go with 2 extremely powerful ARMv8 cores is a very smart one. btw Apple A7 beat Intel Merrifield to the market by 6 months.
There were so many guys going ga ga over Intel Baytrail and even before Intel shipped a single Merrifield phone Apple has matched Baytrail on CPU performance and destroyed it on GPU performance. Apple has delivered a 64 bit CPU with optimized 64 bit OS and apps on launch day. This is the benefit of being a vertically integrated company like Apple which controls every design aspect of their product - CPU core, OS, apps and the phone device. kudos to Apple on the A7 chip and the iPhone 5S