I'm not sold on the idea, here. In most cases, I think more sophisticated procedural textures are a better solution. In the sample image, above, what's really needed is a vector-based texture format (or something better at compressing line art).
Part of the problem with their solution is that even though they solve the problem of video memory, the assets still have to come from somewhere. That means more system RAM, more HDD/SSD space, and more network utilization (either in the form of bigger downloads or if they stream over the net, as mentioned). There's no free lunch, here.
Of course, I can believe there are exceptions, when nothing will work as well as a high-res PBR texture. If any game devs have any examples to share, please do.