AMD could arguably do it. But they have to focus to stay above water at all, and "put 128GB or more of DDR5 ram on any previous-gen GPU" is probably not in their focus. With the state of their software it's not even certain if the community could pick up the slack and turn that into a popular solution.
Their next generation of APUs will have a lot more memory bandwidth and there will probably be lots of AMD APU laptops with 64GB+ of RAM that can use HW acceleration and not be artificially segmented the way Nvidia can do it with VRAM being soldered.