According to Mike "I spoke with an Apple Prototype Developer over at their headquarters (division from Apple known as MediMac) over the phone and discovered that Project N61 is prototype/unreleased iPhone with a moved power button and home button, as well as a lightning connector. iPhone 5 was coded as N41, iPhone 5s was coded as N51, therefore, N61, a letter/number combo I came up with myself, is, without a doubt, the upcoming iPhone 6."
"In the full call, I told the receptionist I was from IL1 (Infinite Loop 1, Cupertino CA) trying to show a representative Project 'N61.' The receptionist transferred me to a higher level of authority at MediMac, which is whom I have included in this video (in terms of the recording.)"
Watch the video to listen to the full recorded phone call & more details.