At 4K we can see that no currently released single GPU can get anywhere close to a 60FPS average or minimum framerate at very high setting, showcasing just how demanding this game ca be when played at higher graphical presets. Please note that this game isn't even maxed out, so performance can plummet further if players want even more visual yum yum.
It is clear that high levels of 4K performance is simply beyond current GPUs in Ghost Recon Wildlands unless they are used in Multi-GPU configurations or with a significant downgrade in visual quality. I'm guessing all of that pre-release 4K 60FPS gameplay was taken on a GTX 1080 Ti SLI setup, as I cannot think of any other setup that could manage such a feat at Ultra settings.