According to the identification code found in the latest macOS Mojave system update, AMD is likely to further expand its Radeon Pro Vega graphics card product lineup for the Mac refresh in early 2019. As reported by Phoronix, patches for Linux kernel drivers were found last Friday which include references to many PCI IDs that do not correspond to the currently available Vega graphics cards
Apple added AMD's Vega 16 and Vega 20 graphics cards to the graphics upgrade options of the new MacBook Pro in mid-November. Although new graphics cards are popular with users who want higher performance, the latest evidence hint that Apple may have begun to consider to introduce these unreleased Vega graphics cards for a future Mac update.
The new Vega 20 PIC ID is determined as 0x66A4, while the Vega 10 version is defined as 0x6869, 0x668A, 0x686B, 0x686D, 0x686E, and 0x686F. Although the new PCI ID strongly suggests that AMD is preparing to release more Vega series in the future, it could perhaps be a variant of existing or upgraded products. It is also possible that these are internal test products are made for compatibility purposes and will not be released.
For Apple, it should be unlikely that a new graphics card option will be added soon after the new units have just been updated. Though Apple used to use laptop parts in the iMac, as the existing product line has not been updated for a long time, so it's a high potential that they could refresh iMac next year.
The new Vega 20 PIC ID is determined as 0x66A4, while the Vega 10 version is defined as 0x6869, 0x668A, 0x686B, 0x686D, 0x686E, and 0x686F. Although the new PCI ID strongly suggests that AMD is preparing to release more Vega series in the future, it could perhaps be a variant of existing or upgraded products. It is also possible that these are internal test products are made for compatibility purposes and will not be released.
For Apple, it should be unlikely that a new graphics card option will be added soon after the new units have just been updated. Though Apple used to use laptop parts in the iMac, as the existing product line has not been updated for a long time, so it's a high potential that they could refresh iMac next year.