A little more update from PC gamer, that the new AI tool will upscale videos between 360p to 1440p.
So for now it seems it cannot upscale 4k video to 8k, but it surly can upscale many 1080p 3D video to 4k, at a much faster rate than the regular AI upscale tools.
I do have a small collection of 1080p 3D videos that needs to be upscale this way. So it's good news anyway.
Meanwhile I am using the "regular" AI tool to upscale Avatar 3D 1 from 1080p to 8k. It'll need 271 hours.