I think the difficulty in wiring means if it happens at all, it'll be soldered CPU + soldered ram. Even if the ram is soldered, having the CPU on a socket would be horrible to manage, but not impossible.
Keep in mind the bandwidths are primarily for the benefit of the integrated GPU, not the CPU. Beyond a point it is effectively unlimited for the CPU cores.
I'm not too familiar with GDDR myself, but the PS5 implementation for example is supposed to be on 256-bit bus. This compares with a typical dual channel consumer mobo reaching 128-bit. So bus width doesn't by itself explain all the difference. Looking it up, even though it is called GDDR, it is actually QDR. So at comparable clocks it should be roughly 4x DDR as we know it.
I have been wondering if the PC space is overdue moving to a unified memory model. The problem with it is that what we expect as upgradable now will unlikely be possible. Not a problem in laptop use cases, but perhaps a harder sell for desktops. I saw speculation that AMD may be bound not to compete with a similar offering to console chips so we might not see this from them. Intel with Arc has the option to do something like that in future.