A modular motherboard design.
I'd like to be able to buy a CPU module, a memory module, or two, or... you get the idea. then buy a vrm module, or even a power supply module, snap them together and then off you go! Literally buy the modules that you need - none of this buy motherboard X for CPU Y made by manufacturer Z.
I'd like to see a standard interface (thunderbolt?) to join together the components and allow us to chain elements to build the computers that we want/need. Forget the ATX standards which seem to be constraining design. Let's see truly modular systems that are expanded as and when the user desires.
It'd probably never happen for many technical reasons, but that would be what I'd like to see. Imagine being able to upgrade your next gen rig by just buying an additional memory "module" and plugging in another 8 DDR4 modules, or even better doubling up the number of cores by adding another CPU module!
I'm sure there are some benefits for the industry there too - the reduction in large scale motherboard parts, simply having interchangeable expansion slots.