Users delving into the latest macOS 10.12.2 beta have discovered strings aligning with potential support for a trio of new GPU families in future hardware — a refreshed Polaris 10, the unknown Polaris 12, and the Vega 10 series.
The code and new KEXT files associated with drivers were found in the latest macOS beta by the Hackintosh community, on the tonymacx86 forums. The last time something like this was discovered, it was the Polaris 11 chipset, which turned out to be the debut of the Radeon Pro 450, 455, and 460 in the Retina MacBook Pro with Touch Bar.
Speculation is running wild, based on little else than the codenames. The Polaris 10 is referred to as the 10XT2, and is probably a process improvement over the existing Polaris 10 series found in the Retina iMac given previous naming conventions.
Polaris 12 is completely unknown at this time.
Some details about the Vega 10 are known. The Vega 10 will be based on AMD's GCN architecture, and the sole offering currently utilizing the nomenclature is more commonly known as the "Fury Pro." At present, the Fury Pro is intended for desktop configurations, like the Mac Pro, and pushes 12 teraflops versus 9 teraflops with the Nvidia 1080 GPU, and has with 16GB of memory, and a 230W thermal design profile.