That's already the nvidia approach, upscaling runs on the tensor cores.

And no it's not something magical it's just matrix math. AI workloads are lots of convolutions on gigantic, low-precision, floating point matrices. Low-precision because neural networks are robust against random perturbation and more rounding is exactly that, random perturbations, there's no point in spending electricity and heat on high precision if it doesn't make the output any better.

The kicker? Those tensor cores are less complicated than ordinary GPU cores. For general-purpose hardware and that also includes consumer-grade GPUs it's way more sensible to make sure the ALUs can deal with 8-bit floats and leave everything else the same. That stuff is going to be standard by the next generation of even potatoes: Every SoC with an included GPU has enough oomph to sensibly run reasonable inference loads. And with "reasonable" I mean actually quite big, as far as I'm aware e.g. firefox's inbuilt translation runs on the CPU, the models are small enough.

Nvidia OTOH is very much in the market for AI accelerators and figured it could corner the upscaling market and sell another new generation of cards by making their software rely on those cores even though it could run on the other cores. As AMD demonstrated, their stuff also runs on nvidia hardware.

What's actually special sauce in that area are the RT cores, that is, accelerators for ray casting though BSP trees. That's indeed specialised hardware but those things are nowhere near fast enough to compute enough rays for even remotely tolerable outputs which is where all that upscaling/denoising comes into play.