DLSS does not require any specific packaging configuration. There's no reason DLSS can't run on DGX Spark or GPU cores of the Apple's M-chips aside from specific Nvidia software optimizations that can surely be worked out if needed.

I imagine the PCs for the future would maybe have motherboard with two sockets: a normal CPU one and a GPU one, both having access to some high bandwidth unified memory that.

Right now the unified memory needs to be pretty much soldered super close to the chip to ensure the bandwidth and energy efficiency, but hopefully there will be some solution to circumvent this limitation in the future.

Putting CPU and GPU cores into the same physical die works for your average consumer machines, but hardcore professionals or enthusiasts would always strive for more custom configurations than existing packages can provide, like more GPU cores.