Despite the missing part, Apple is obviously close enough to mass production that it has scheduled an event for September 9th. At that time, Apple is expected to officially introduce the 4.7 inch device, and release launch dates, pricing and specs.
The motherboard is usually one of the last pictures we see of an upcoming iPhone, before the phone is unwrapped. Earlier this week, we passed along information that the handset is undergoing Product Validation Testing. Mass production usually follows.
source: NWE (translated) via GSMArena