The desktop Kaby Lake processors will be released later this year but AMD hasn't given any information regarding Polaris GPUs. Apple could: Keep the same GPU options. Use the re-branded 300 series GPUs (however there are only 3). Use Nvidia. Announce it and release it later this year/next year. Announce it at the March event next year. I hope they use Nvidia as the iMac will truly have a desktop GPU, however I don't mind waiting until next year as long as the graphics are upgraded. Since we are due for a redesign, it seems likely that they'll upgrade to the 14nm GPUs in order to allow for the new design.