A few weeks ago in some regions became available to the MacBook Pro 2018 with discrete graphics Radeon Pro Vega 16 and Vega Pro 20. However, if you believe reports in the near future, advanced video cards may appear in other Apple computers. In particular, in the iMac.
According to the authors of the publication Photonix, who noticed in one of the technical patches associated with Linux drivers mention new AMD Vega. Such references then appeared in macOS Mojave. In this case the PCI IDs of components do not coincide with those that are already being used in Apple computers.
Thus, it is possible to talk about the fact that Apple has already started the preparation of new computers, which will differ from its predecessors primarily advanced discrete graphics.
It is expected that the official announcement of new versions will be held next spring.