While the world cheers on 4K resolution, and some manufacturers have even introduced 8K displays—like this insane Dell UltraSharp—a little detail slipped through HDMI's official 2.1 spec sheet: it'll support 10K resolution at a full 120Hz refresh rate.
Initially introduced in January of this year, HDMI's huge 48 Gbps bandwidth was heralded as being 8K 120Hz capable, which is more resolution than any current GPU can handle. We even reported on it here. A look back at the spec overview, however, shows that 10K resolutions are possible at 50Hz, 60Hz, 100Hz and 120Hz.
The problem is driving that many pixels. Current GPUs like the GTX 1080 Ti, our pick for the best high-end graphics card, can usually maintain 4K at 60 fps in current games, perhaps with a few tweaks to the settings. 5K is 78 percent more pixels than 4K, and 10K is four times as many pixels as 5K. Then double the performance requirements again to hit 120 fps. That would be more than 14 times as many pixels as 4K, or more than 55 times as many pixels as 1080p.
If we assume a somewhat generous increase in GPU performance of 30 percent per year, it will take about ten years before GPUs are fast enough to handle 10K panels at 120 fps in games. Film and other media would be much easier, but even the current HEVC specifications don't go beyond 8K at 60 fps.
There's still the question of what to do with those pixels. A 27-inch 4K display has around 160 DPI, and from a distance of more than a couple of feet, most of us aren't equipped with eyes that are good enough to resolve the individual pixels. You could have a 10K screen with a 73-inch diagonal and get a similar DPI. Theoretically, 10K would be a great resolution for truly incredible VR, but again that's only if the pixels can be rendered fast enough (minimum 90Hz, possibly a lot higher).
There's no word on when devices supporting 10K at 120Hz will start coming out, but given the above limitations, don't expect to upgrade anytime soon. But your kids or grandkids will love it.