It sounds to me like this is not so much “end of the desktop PC” as it is “end of the removable CPU”. Just another step in the evolution that has brought us from the days when a PC wouldn’t work without an array of cards plugged into ISA slots.
Higher integration of the CPU onto the mobo isn’t going to preclude someone from packaging it up as a desktop if they want to. It will just look a lot like a laptop inside a bigger case. Expansion is all going to be via USB and DisplayPort anyhow so I see this as a non-story, just as when they started integrating other bits and pieces of the traditional PC.
Intel will be building the MoBo’s.