It seems that Apple has begun negotiations with a number of companies that are able to build the following 3D camera sensors such as Infineon Technologies, Sony, Panasonic and STMicroelectronics NV.
See also: How does Face ID of Apple work?
AR became Apple's top priority and CEO Tim Cook, the goal of bringing Apple to become a leader in the industry with completely new technology at this launch.
Bloomberg also said that the new 3D sensor is still in its infancy so it may be delayed or abandoned. The goal is for 2019, Apple will have both Face ID and 3D sensors for the new rear camera on the iPhone, as part of the AR promotion effort they are pursuing for their long-term plans.