There is still lot of productivity stuff that benefits from power of desktops. Engineering (Ansys etc), local AI development, 3D modeling, working with large C++/Rust codebases, scientific computing, etc etc. And related to gaming there is of course the huge game developer market too. There is a reason why nvidia and amd still make workstation class GPUs for big bucks.
But all of that hinges on fast off-chip memory. If manufacturers agree that this memory and the SoC need to be soldered, there's not much left to swap out except PCIe boards.
