Apple is reportedly introducing support for a new connector type in its MFi (Made for iPhone) licensing program for certified accessories. Apple calls it the Ultra Accessory Connector (UAC) and it's much smaller than the USB Type-C and Lightning connectors currently used by the company. It is used for the same purposes as all connectors - for charging and transferring data - and will reportedly replace Lightning and USB connectors in some cases.
The UAC connector is similar to the ones found on Nikon cameras, and this support will allow licensees to make Lightning to UAC, USB-A to UAC, and 3.5mm headset jacks to UAC cables, for connecting various Apple devices - though currently the only use specified by the company is between Apple devices and headphones. 9to5Mac reports that "the UAC will allow accessory makers to save space inside their designs versus using an Apple Lightning port or USB-C, which are similar in size to one another."
The UAC connector measures in at 2.05mm by 4.85mm at the tip, and is slightly less thick and half as wide as the USB Type-C and Lightning port.
Because of this new port support, speculations of Apple introducing a new kind of connector have started to do the rounds. However, Ars Technica says that Apple has confirmed "it was adding the port to the MFi program at the request of licensees, not because it's trying to push licensees to support a new kind of connector."
So far, the UAC specs are available in developer preview only to preparing manufacturers of the change. It wouldn't be a smart move on Apple's part to introduce a new port right now, as it just shifted to USB Type-C and Thunderbolt 3 ports on its MacBook Pro 2016 models. Apple also removed the 3.5mm audio jack on the iPhone 7 and iPhone 7 Plus forcing users to use the Lightning port for charging and audio. It is unlikely that Apple will introduce UAC as a replacement to either USB Type-C or Lightning port.