According to 9to5Mac Apple is working on a new kind of iDevice connector-- the "Ultra Accessory Connector," (UAC) reportedly a new application for an old 8-pin plug.
Apparently released in developer preview form through the Made-for-iPhone (MFi) licensing program, the UAC connector is small connector measuring 2.05mm x 4.85mm, making it slightly thinner than USB-C and nearly half as wide as USB-C and Lightning. It is essentially identical to the ultra-mini USB connectors found in proprietary cables bundled with devices such as Nikon cameras (pictured).
But what use will be the use of UAC plugs? As an intermediary, mainly. The unnamed 9to5Mac sources say UAC is not be a Lightning replacement. Instead it provides cross-compatibility between multiple connector types. Thus, users can swap between Lightning-to-UAC and USB-to-UAC cables with the same pair of headphones, with UAC allowing device firmware to juggle between connectors on the fly.