Superresolution. You have a lower resolution animation (less pixels = less calculations) and then use superresolution to turn that into a 4K image. This is reality right now for NVIDIA GPUs ( I think itβs called DMSS)
There is one out there from 5 years ago or so that is similar to Google's Seurat but for animated stuff, I think pre-baking triangle culling for different views within a limited volume. I can't remember the name of it, from the details I remember (there was a realistic orangutan or something like that rendered with fur) I should be able to find it on Google, but Google search has become degraded recently.
Nvidia DLSS is an important part of how they achieved 30Hz at 4k resolution, but that's more of a shading assist and doesn't affect the animation. The facial animation will be compressed with Ziva's ML solution.
