it took a bit of seeking, but entries of AMDs next-gen Navi has surfaced in the Mojave MacOS version 14.2 as website Tonymacx86 spotted. As mentioned it took a bit of seeking, as the entries are located in actual programming code.
A file that is called AMDRadeon6000HWServiceskext has "Navi" listed in several segments of the code. Not just that, four models have been spotted: Navi 16, Navi 12, Navi 10 and Navi 9. The number could be related to the number of computeunits.
If AMD continues to use 64 shaders per compute unit in Navi, it means that the smallest discrete Navi GPU has been limited to 576 shader units in an aim to replace the Radeon RX 540, the Radeon RX 550, the Radeon RX 560 and all related mobile GPUs. Navi 16 would get 1024 Shader processors. Videocardz mentions these are likely names for different products, not the names of the GPUs. The device ID for NAVi was listed as 0x73101002.
If added to the code, logic assumes a lucnh is pending this year similar to when Apple added Vega's code to MacOS Sierra, after which Vega was launched I think it was six months later. So who knows, Navi within six months?